Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF MAKING AN TNJECTION MOLDING NOZZLE
WITM A MEATING ELEMENT EXTENDING OUTWARD
BETWEEN ADJACENT COLLAR PORTIONS
BACKGROUNp OF THE INVENTION
This invention relates generally to injection
molding and more particularly to a method of making an
integral nozzle with an integral heating element extending
outward between adjacent collar portions.
Injection molding nozzles having a helical
integral electrical heating element extending around the
central melt bore are well known in the art. As seen in
the applicant's U.S. patent number x,865,535 which issued
September 12, 1989, it is also known to have a portion of
the heating element swaged back upon itself to provide more
heat in certain areas, Of course, each nozzle must have a
terminal to which external lead wires are connected to
provide power to the heating element. In the past, this
has usually been provided by the heating element having end
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portions which extend outward through a radial opening in
a collar portion adjacent the rear end of the nozzle. An
example of this is seen in the applicant's U.S. patent
number 4,386,262 which issued May 31, 1983. In this ease,
a so called "hot" terminal is formed by casting beryllium
copper around the heating element in a radially extending
sleeve. While this terminal is structurally sound, it has
the disadvantage that the terminal is too hot which results
in possible damage due to overheating of the external lead
wires or other adjacent materials. Another example of the
end portions of the heating element extending outward
through an opening in the collar portion is shown in the
applicant's U.S. patent number 4,403,405 which issued
September 13, 1983. In this case, half washers mounted in
the opening around the heating element prevent the
conductive beryllium copper flowing out into the terminal.
While this overcames the problem of the terminal
overheating and thus is a so called '°cold" terminal, it has
the disadvantage that the terminal is not as strong
structurally and it is difficult to ensure the terminal
extends straight out from the nozzle.
Another example of a method of making a terminal
in which the end portion of a heating element has to be run
out through a hole in the collar portion is described in
the applicant's U.S. patent number 4,837,925 which issued
June 13, 1989. However, it is relatively easy to
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manipulate the end portion of the heating element because
it is a low voltage application with the other end of the
heating element grounded to the nozzle body and thus there
is only a single terminal wire extending to the terminal.
Reliable terminals having two terminal wires are more
difficult to make than terminals having only a single
terminal wire because it is important that the two
projecting terminal wires of the heating element extend
parallel to each other and are spaced apart a predetermined
distance. Also, the terminal must be structurally secure
and relatively easy to manufacture without requiring two
different brazing steps.
SUMMARY OF' THE INVENTION
Accordingly, it is an object of the present
invention to at least partially overcome the disadvantages
of the prior art by providing a method of making an
integral nozzle with a heating element extending outward
between adjacent collar portions.
Another object of the invention is to provide a
method of making an integral nozzle with a structurally
secure terminal wherein two 'terminal wires of the heating
element are spaced a predetermined distance apart and
extend parallel to each other radially outward from the
body of the nozzle.
To this end, in one of its aspects, the invention
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provides a method of making an injection molding nozzle
including the steps of making an elongated steel outer body
with a rear end, a forward end, a generally cylindrical
outer surface, and a melt bore extending centrally
therethrough from the rear end to the forward end, and
integrally vacuum brazing an insulated electric heating
element in a spiral channel in the outer surface of the
body, the heating element having an insulated heating wire
extending in an outer casing, the improvement comprising
the further steps of:
(a) winding the heating element in the spiral
channel with at least one end portion projecting radially
outward from the channel near the rear end of the outer
body of the nozzle,
(b) making a steel forward collar portion with
a rear face and a circular opening extending centrally
therethrough, the circular opening having a predetermined
diameter to fit over the outer surface of the outer body of
the nozzle,
(c) making a steel rearward collar portion with
a rear face, a forward face, and a circular opening
extending centrally therethrough, the circular opening
having a predetermined diameter to fit over the outer
surface of the outer body of the nozzle, making at least
one of the forward collar portion and 'the rearward collar
portion whereby a radial opening is formed between the
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forward collar portion and rearward collar portion when the
forward face of the rearward collar portion abuts against
the rearward face of the forward collar portion,
(d) mounting the forward collar portion around
the outer surface of the outer body of the nozzle in a
position adjacent the at least one projecting end portion
of the heating element,
(e) mounting the rearward collar portion around
the outer surface of the outer body of the nozzle with the
forward face of the rearward collar portion abutting
against the rearward face of the forward collar portion and
the at least one end portion of the heating element
projecting radially out through the radial opening formed
between the forward collar portion and the rearward collar
portion,
(f) making a steel stud portion having an inner
end, an outer end, and at least one bore extending through
the stud portion from the inner end to receive the at least
one projecting end portion of the heating element,
(g) mounting the steel stud portion to extend
radially outward from the radial opening formed between the
forward collar portion and the rearward collar portion with
the at least one portion of the heating element extending
outwardly a predetermined distance through the at least one
bore in the stud portion,
(h) applying brazing material along the joins
between the outer body, forward collar portion, rearward
collar portion, and stud portion, and around the at least
one end portion of the heating element extending through
the at least one bore in the stud portion, and
(i) heating the assembled outer body, heating
element, forward collar portion, rearward collar portion,
and stud portion above the melting temperature of the
brazing material in a reduced oxygen atmosphere in a vacuum
furnace according to a predetermined cycle to melt the
brazing material and integrally braze thA outer body,
heating element, forward collar portion, rearward collar
portion, and stud portion together to form a
metallurgically monolithic nozzle.
BRIEF DESCRIPTTON OF THE DRAWINGS
Figure 1 is an exploded isometric view of
components of the nozzle illustrating some of the steps of
making the nozzle according to a preferred embodiment of
the invention,
Figure 2 is a schematic view illustrating one
pattern of the heating element channel around the outer
surface of the nozzle body, and
Figure 3 is a cut-away isometric view showing
additional components to illustrate further steps of making
the terminal according to this embodiment of the invention,
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and
Figure 4 is a cut-away isometric view similar to
Figure 3 showing the steps of making the nozzle according
to another embodiment of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is first made to Figure 1 which shows
components of an injection molding nozzle having a double
channel and a terminal for 'two terminal wires and how they
are assembled. An elongated outer body 10 having a central
melt bore 12 extending from a rear end 1~ to a forward end
16 is made of tool steel. While the nozzle body 10
illustrated in this embodiment is made of one piece, it may
also be made by joining several longitudinal sections to
provide different selected sizes and lengths as described
in the applicant's U.S. patent number 4,945,630 which
issued August 7, 1990. The nozzle body 10 is made with a
spiral channel 18 extending around its outer surface 20.
The spiral channel 18 is a double channel which extends
rearwardly from a U-shaped bend portion 21 adjacent the
forward end 16 of the nozzle body 10. As illustrated in
Figure 2, the double channel 18 is made with a
predetermined pattern to vary the amount of heat provided
along the surface 20 of the nozzle body 10 according to the
reguirements of the system, In this embodiment, the double
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spiral channel 18 is more concentrated near the rear and
forward ends 14, 16 of the outer body 10 so more heat is
provided in those areas than in the middle of the body 10.
While the outer surface 20 of the nozzle body 10 is
generally cylindrical, in this embodiment it is made with
a bevel 22 at the forward end 16, and a reduced diameter
portion 24 extending from an inwardly extending seat 26
adjacent the rear end 14. An electrical heating element 28
is wound in the double spiral channel 18 with a U-shaped
bend 29 received in the U-shaped bend portion 21 of 'the
channel 18 and two end portions 30 projecting radially
outward near the rear end 14 of the body 10 to two ends 32.
As is well known in the art, the heating element 28 has a
thin heating wire 34 which extends through an insulating
material 36 such as magnesium oxide inside a steel casing
38. The heating wire 34 is connected to a terminal wire 40
at each end 32. The two terminal wires 40 have a much
larger diameter than the thin heating wire 34 so they are
not hot. In this embodiment, the outer casing 38 has been
stripped back slightly further than the insulating material
to avoid any possibility of electrical shorting occurring
between the heating wire 34 and the surrounding outer
casing 38. A thin hollow thermocouple tube 42 is tack
welded to the outer surface 20 of the body 10 over the
heating element 28 to extend longitudinally to a
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thermocouple bore 44 w~iich is machined diagonally into the
body 10 of the nozzle adjacent its forward end 16.
A forward collar portion 46 is made of steel with
a circular opening 48 of a predetermined diameter to fit
over the outer surface 20 of the outer body 10. In this
embodiment, the forward collar portion 46 is made with an
inwardly extending rear flange portion 50 which forms a
rear face 52 and an insulation flange portion 54 which
extends forwardly from the rear flange portion 50. In 'this
embodiment, the rear face 52 of the forward collar portion
46 is made with an inner segment 56 and an outer segment 58
of two seats which are described in more detail below. The
forward collar portion 46 is mounted around the body 10
with the seat segments 56, 58 adjacent to and aligned with
the two projecting end portions 30 of the heating element
28. If the forward collar portion 46 is made with a
circular opening 48 which fits over the reduced diameter
portion 24 of the outer surface 20, but is too small to
slide over the forward end 16 of the body 10, it is mounted
from the rear by moving it inwardly on an angle over the
projecting end portions 30 of the heating element 28 and
then turning it forwardly over the rear end 14 of the body
10.
A rearward collar portion 60 is made of steel
with a circular opening 62 extending centrally from a rear
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face 64 to a forward face 66. In this embodiment, the
circular opening 62 is made to fit around the reduced
diameter portion 24 of the outer surface 20 of the body 10
and the collar portion 60 is made with an inwardly
extending flange portion 68 which fits in the inwardly
extending seat 26 at the rear end 14 of the body 10. Also,
the forward face' 66 of the rearward collar portion 60 is
made with a forwardly extending inner rim 70 which
interlocks with the rear face 52 of the forward collar
portion 46 when they abut against each other. Of course,
in other embodiments, the outer surface 20 of the body 10,
the forward collar portion 46, and the rearward collar
portion 60 can be made with different suitable shapes which
fit together. The rearward collar portion 60 is made with
a radial slot 72 therethrough extending longitudinally away
from the forward face 66. The outer wall 74 of the
rearward collar portion 60 has an inner seat 76 and a
larger outer seat 78 which extend around the longitudinal
slot 72. These outwardly open seats 76, 78 in the rearward
collar portion 60 are made circular, except that, in this
embodiment, a portion of each of them is formed by the
matching inner and outer seat segments 56, 58 in the rear
face 52 of the forward collar portion 46. The rearward
collar portion 60 is made with the rear face 64 having a
slot 80 to receive a thermocouple wire and threaded bolt
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holes 82 to receive bolts (not shown) for mounting
purposes. The rearward collar portion 60 is mounted over
the rear end 14 of the body 10 with the seats 76, 78 around
the longitudinal slot 72 aligned with the seat segments 56,
58 in the forward collar portion 46. The forward face 66
abuts against the rear face 52 of the forward collar
portion 46 with which the inner rim 70 interlocks to ensure
proper location. The inwardly extending flange portion 68
is received in the seat 26 around the rear end 14 of the
body 10 with the rear face 64 of the rearward collar
portion 60 flush with the rear end 14 of the body 10. The
end portions 30 of the heating element 28 extend outwardly
through the slot 72 in the rearward collar portion 60, and
the inner and outer circular seats 76, 78 around the slot
72 are partially formed by each of the forward and rearward
collar portions 46, 60. In other embodiments, the forward
and rearward collar portions 46, 60 may be made to combine
differently to form the slot 72 or a different shaped
opening between them
A stud portion 84 is made of steel with two bores
86 extending from the inner end 88 to a central bore 90
extending from the outer end 92. The two bores 86 extend
parallel to each other and are spaced apart a predetermined
distance. Each bore 86 is just large enough to fit over
one of the outwardly extending end portions 30 of 'the
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heating element 28. While the stud portion 84 is made
generally cylindrical, it has a smaller diameter neck
portion 94 at the inner end 88 which fits in the inner seat
76 around the longitudinal slot 72. As seen in Figure 2,
the stud portion 84 is mounted with the neck portion 94 at
its inner end 88 seated in the inner seat 76 around the
slot 72, and the end portions 30 of the heating element 28
extending through the two parallel bores 86. This
structurally supports the outwardly projecting end portions
30 of the heating element 28 and ensures that they extend
radially outward and are parallel and spaced apart a
predetermined distance.
When the components described above are mounted
together as seen in Figure 3, brazing material such as
nickel alloy paste is applied along the joins between them
and around the two end portions 30 of the heating element
28 which extend through the two bores 86 of the stud
portion 84. Brazing material is also applied along the
heating element 28 wound in the spiral channel 18 similar
to the description in the applicant's U.S. patent number
4,557,685 which issued December 10, 1985. The assembly is
then inserted into a vacuum furnace (not shown) and heated
above the melting temperature of the brazing material
according to a predetermined cycle. As the furnace is
gradually heated, it is evacuated to a relatively high
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vacuum to remove nearly all of the oxygen. Before the
melting temperature of the brazing material is reached, the
vacuum is reduced by partially backfilling with an inert
gas such as argon or nitrogen. When the nickel alloy
brazing material melts, it flaws by capillary action along
the joins between the components and around the heating
element 28 to completely embed it in the channel 18. This
brazing in the vacuum furnace provides a metallurgical
bonding of the nickel alloy to the steel of the various
components to form a metallurgically monolithic integral
heated nozzle 96. After the nozzle 96 is cooled and
removed from the vacuum furnace, it is machined to provide
a smooth outer finish. A thermocouple bore (not shown) is
machined through the forward and rearward collar portions
48, 60 to connect the thermocouple slot 80 in the rear face
66 of the rearward collar portion 60 to the thermocouple
tube 42 which is now also integrally brazed along the outer
surface 20 of the body 10. As seen in Figure 3, a
thermocouple wire 97 is then inserted through this
thermacouple bore and thermocouple tube 42 and bent
outwardly through the thermocouple slot 80 to monitor the
operating temperature adjacent the forward end 16 of the
body 10.
Referring more specifically to Figure 3, a pair
of elongated metal connectors 98 are made each having an
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4~~c~
inner end 100, an outer end 102, a cylindrical outer
surface 104, and a longitudinal bore 106 large enough to
receive bare electrical caires therein. Each connector 98
is also made with inner and outer longitudinally spaced
threaded bores 108, 110 extending from the longitudinal
bore 106 to the outer surface 104. Each connector 98 is
mounted over the end 32 of one of the radially projecting
end portions 30 of the heating element 28 with the bared
wire portion 40 extending from the inner end 100 of the
connector 98 into the longitudinal bore 106 past the inner
threaded transverse bore 108.
An insulator 112 having an inner end 114, outer
end 115, and a cylindrical outer surface 118 is made of a
suitable ceramic insulating material. The insulator 112 is
also made with two spaced parallel longitudinal bores 120
and twa longitudinally spaced transverse openings 122
extending from each longitudinal bore 120 to the outer
surface 118. Tire insulator 112 is mounted over the
projecting connectors 98 with its inner end 114 received in
the central bore 90 of the stud portion 84. Each of the
metal connectors 98 is received in one of the longitudinal
bores 120 of the insulator 112 with the threaded transverse
bores 108, 110 in the connectors 98 aligned with the
transverse openings 122 in the insulator 112. A set screw
124 is then inserted through each transverse opening 122 in
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the insulator 112 into the aligned threaded transverse bore
108, 110 in the connectors 98, and the set screws in the
inner threaded bores 108 of the connectors 98 are tightened
on the bared wire portions 40 of the projecting end
portions 30 of the heating element 28 to securely connect
each connector 98 to one and 32 of the heating element 28.
Alternatively, the connectors 98 can first be inserted into
the insulator 112 and then connected to the ends 32 o:E the
heating element 28.
As seen in Figure 3, a bared end 126 of an
electrical external lead wire 128 can be inserted into the
longitudinal bore 106 of each metal connector 98 from the
outer end 102 past the outer threaded transverse bore 110.
'Ihe set screw 124 in each outer threaded bore 110 is then
tightened to securely connect the lead wires 128 to the
connector 98. It will be appreciated that the lengths of
the bared wire portions 40 of the end portions 30 of the
heating element 28, the bared ends 126 of the lead wires
128, and the connectors 98 must be predetermined to ensure
they are securely connected together. Also, the lengths of
the end portions 30 of the heating element 28, the stud
portion 84, and the insulator 112 must also be
predetermined to ensure the metal connectors 98 are
entirely inside the insulator 112. Finally, a hollow
protective terminal sleeve 130 which was previously located
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over the lead wires 128 is mounted to extend outwardly from
the stud portion 84 around the insulator 112. The
protective sleeve 130 has a threaded inner end 132 which is
screwed over the threaded stud portion 84 into the outer
seat 78 around the longitudinal slot 72. In addition to
protecting the connectors 98 and insulator 112, this adds
structural strength to the terminal to prevent it getting
bent from its correct position.
In use, a gate insert 134 or nozzle seal which is
shaped to provide a desired gating configuration is mounted
in the forward end 16 of the completed nozzle 96. One or
more nozzles 96 are mounted in a suitable mold with the
insulation flange portion 54 received in a suitable seat in
a cavity plate to locate and support the nozzle. The
insulation flange portion 54 which extends forwardly is
spaced outwardly a predetermined distance from the outer
surface 20 of the body 10 to provide thermal insulation to
avoid excessive heat loss. Electrical power is provided to
the heating element 28 of each nozzle 96 through the lead
wires 128 to heat them to a predetermined operating
temperature. Pressurized melt from a molding machine is
then injected to flow through the central bore 12 of the
body 10 of each nozzle 96 and into cavities through the
adjacent gates. After the cavities are filled, injection
pressure is held momentarily to pack and 'then released.
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After a short cooling period, the mold is opened to eject
the molded products. After ejection, the mold is closed
and injection pressure is reapplied to refill the cavities.
This cycle is continuously repeated with a frequency
dependent on the size and shape of the cavities and the
type of material being molded.
Reference is now made to Figure 4 to describe a
method of making an injection molding nozzle according to
another embodiment of the invention. As some of the
LO elements are the same or similar to those described above,
common elements are described and illustrated using the
same reference numerals. In this embodiment, the heating
element 28 is made with a double heating wire 136 extending
in the insulating material 36 in a single casing 38. Thus,
L5 rather than the entire heating element 28 including the
casing 38 being made with a U-shaped bend, only the heating
wire 136 itself has a U-shaped bend (not shown) near the
forward end 16 of the nazzle body 10. The double heating
wire 136 is connected to two larger diameter terminal wires
40 which project outwardly to two ends 32 from a single end
portion 138 of the heating element 28 which extends
radially outward near the rear end 14 of the body 10 of the
nozzle.
The forward collar portion 46 and rearward collar
~5 portion 60 are made as described above and mounted with the
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single end portion 138 of the heating element 28 extending
out through the opening 140 between them. In this
embodiment, the steel stud portion 142 is made with only a
single bore 144 extending therethrough and with a threaded
portion 146 extending from the outer end 148 to a small
circumferential flange 150. The stud portion 142 is
mounted in the seat 76 in the forward and rearward collar
portions 46, 60 with the single end portion 138 extending
out through the single bore 144. The assembly is then
integrally brazed together .in a vacuum furnace as described
above.
In this embodiment, a generally cylindrical
ceramic spacer portion 152 is made with a small
circumferential flange 154 and two parallel bores 156
spaced a predetermined distance apart extending from an
inner end 158 to an outer end 160. The spacer portion 152
is securely mounted by ceramic paste in the stud portion
142 with the flange 154 abutting against the outer end 148
of the stud portion 142. As can be seen, the two terminal
wires 40 extending from the single end portion 138 of the
heating element 28 diverge in a space 162 in the stud
portion 142 where they are surrounded by ceramic paste and
then extend out through the two parallel bores 156 in the
spacer portion 152.
In use, the connection of the two electrical lead
20~~'~'~~
wires 128 is completed using a disc shaped silicon rubber
seal 164 and a ceramic insulative sleeve 166 which fit in
a threaded steel cap 168. The seal 164 fits in an opening
170 in the outer end of the cap 168, and the seal 164 and
the insulative sleeve 166 have a pair of spaced parallel
bores 172 extending therethrough to receive the two lead
wires 128. The cap 168, seal 164, and insulative sleeve
166 slide up the lead wires 128 out of the way and the lead
wires 128 are then fastened to the projecting terminal
wires 40 of the heating element 28 by electrical crimps
174. The sleeve 166, seal 164, and cap 168 are then slid
down into place around the crimps 174 and the threaded cap
168 is tightened onto the threaded stud portion 142. The
silicon rubber seal 164 prevents moisture entering the
terminal, and this arrangement has excellent structural
strength and facilitates connecting and disconnecting the
lead wires 128 to the nozzle.
While the description of making the heated
manifold has been given with respect to preferred
embodiments, it will be evident that various modifications
are possible without departing from the scope of the
(invention as understood by those skilled in the art and as
defined in the following claims. For instance, in another
embodiment the heating element 28 is made with the casing
38 having a sharp U-shaped bend so the outward and return
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casing 38 both extend in side by side contact in a single
spiral channel 18.
