Gas nozzle for a gas assisted injection molding system

A gas nozzle for a gas assisted injection molding system includes a body having an inlet in fluid communication with a source of pressurized gas, an outlet through which gas leaves the nozzle and a passage extending between the inlet and the outlet. The outlet includes a plurality of apertures wherein at least some of the plurality of apertures have a rectangular shape arranged such that the longitudinal axis of consecutive rectangular shaped apertures are parallel to one another and such that the flow path through the outlet approximates a 1/8 inch hole but does not clog with resin over successive plastic injections into the mold.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The present invention relates, generally, to a gas assisted injection 
molding system. More specifically, the invention relates to a gas nozzle 
employed in such systems. 
2. Description of the Related Art 
Gas assisted plastic injection molding is a well established and 
commercially accepted method for providing plastic articles having a 
hollow interior. These hollow, plastic articles have numerous advantages, 
such as high strength, low weight, reduced plastic material cost and 
improved article appearance due to less shrinkage stress. A detailed 
discussion of the development of gas assisted injection molding technology 
is contained in U.S. Pat. No. 5,110,533 and incorporated herein by 
reference. 
In gas assisted injection molding, the articles are produced by injecting 
molten resin into the mold cavity and injecting a quantity of pressurized 
gas into the resin to fill out the mold cavity and form a hollow portion 
in the resin. The gas is preferably an inert gas such as nitrogen. The gas 
pressure is maintained in the mold cavity and against the resin until the 
plastic has cooled sufficiently to be self supporting. Thereafter, the gas 
is vented, the mold is opened and the plastic article is removed from the 
cavity. One example of a gas assisted molding method and apparatus is 
disclosed in my U.S. Pat. No. 5,639,405 issued on Jun. 17, 1997 and 
incorporated herein by reference. 
Generally speaking, there are two points of entry for gas in an injection 
molding environment: (1) at the injection molding machine nozzle; and (2) 
in the mold. 
When the gas is injected through the same nozzle employed for injecting the 
plastic into the mold, the gas pressure must be relatively high because 
the gas bubble will not penetrate the plastic until the gas pressure is 
greater than the plastic injection pressure. In addition, any restriction 
such as at the gate will impede the bubble penetration requiring higher 
initial gas pressures to move the plastic to fill out the mold. However, 
when the pressure is too high, and once the bubble breaks through the 
gate, the gas will rocket through the cavity which is at a lower pressure 
to the end of the plastic flow front. If this occurs, the gas may escape 
the envelope of the plastic material unless there is extra resin in the 
cavity to resist this high pressure. Such elevated initial gas pressures 
at the plastic injection nozzle may wash away most of the plastic that is 
adjacent the gate including the material at the nominal wall. Gas 
injection at the plastic nozzle also requires complicated resin shut-off 
devices, valves and sealing members which ultimately wear out and are 
generally expensive. 
On the other hand, gas may be injected directly into the mold at either the 
mold cavity (in-article) or at some point along the runner (in-runner). 
Where gas is injected directly into the mold cavity, the initial gas 
pressure at the beginning of the gas filling phase of the process can be 
much lower than that employed at the resin injection nozzle. The lower gas 
pressure will tend to complete the polymer fill at a velocity that is 
closer to the initial polymer fill velocity, thereby avoiding a gloss 
variation between initial polymer fill and gas pressure fill. Gas nozzles 
located in the runner are advantageous where the design of the part or 
structure of the mold does not lend itself to the in-article approach. 
Numerous gas nozzles have been proposed in the related art to take 
advantage of the design and engineering advantage of mold cavity and 
runner gas injection. For example, stationary gas nozzles have been 
employed in the related art because such nozzles generally involve a 
reduction or elimination of any moving parts. Such stationary nozzles are 
simple and cost effective. However, stationary nozzles suffer from the 
disadvantage that they often become clogged with resin during the 
injection process and must be cleaned on a regular basis. 
In order to overcome this problem, gas nozzle designers have incorporated 
resin check valves to block the flow of molten resin into the gas nozzle. 
Unfortunately, these resin check valves increase the cost and complexity 
of such nozzles. 
Another solution proposed in the related art involves a hollow gas nozzle 
with an interior solid pin that has been relieved on a portion of one side 
to allow for a gas passage through the nozzle. Unfortunately, problems 
still exist with such nozzles of the related art. More specifically, these 
gas nozzles are typically mounted from the back side of the mold which is 
fixedly mounted to the platen of an injection molding press. If the mold 
is overshot during the injection process, as can frequently be the case, 
excessive injection pressure can clog the nozzle with resin. In this case, 
the mold must be removed from the platen and the gas nozzle disassembled 
and cleaned. Further, gas may exit such nozzles only through the top or 
terminal end thereof which is a limiting factor in the design of the part 
and the mold. Finally, larger parts often require a larger volume of gas 
flow and the relieved area of the gas nozzle does not accommodate this 
larger volume. 
Additionally, the nozzles of the related art discussed above suffer from 
the disadvantage that once they are connected to a source of pressurized 
gas, such as when mounted in the mold or runner, they are not easily 
adjusted thereafter. This disadvantage is particularly apparent when the 
direction of the flow of gas from the nozzle is important. This often 
occurs when it is desirable to direct the flow of gas in a particular way 
into the mold and the gas nozzle includes an outlet which extends 
generally perpendicular to the main flow passage of the nozzle or out the 
side of the nozzle tip. 
Thus, there is a need in the art for a simple, cost effective, efficient, 
stationary gas nozzle which includes no moving parts and which will not 
clog with resin during polymer fill or gas venting even after repeated 
shots of the mold. 
SUMMARY OF THE INVENTION 
The present invention overcomes the disadvantages in the related art in a 
gas nozzle assembly for a gas assisted injection molding system. More 
specifically. the gas nozzle of the present invention includes a body 
having an inlet in fluid communication with a source of pressurized gas, 
an outlet through which gas leave the nozzle and a passage extending 
between the inlet and the outlet. The outlet includes a plurality of 
apertures wherein at least some of the apertures have rectangular shape 
arranged such that the longitudinal axis of consecutive rectangular shaped 
apertures are parallel to one another. Alternatively, the rectangularly 
shaped apertures may be arranged in such a way that the apertures 
approximate a radial pattern about a common centerpoint and such that the 
longitudinal axis of radially spaced rectangular shaped apertures are 
parallel to one another. 
The plurality of rectangular shaped apertures, while individually very 
small, provide a flow passage for the gas which approximates the flow path 
(but not volume) of gas through a hole having a diameter of between 0.055 
to 0.125 inches. And while the molten resin may form a "skin" over the 
outlet at the completion of a molding cycle, the individual apertures are 
sufficiently small such that they do not become clogged. Further, the 
"skin" covering the plurality of apertures is easily blown off during the 
next injection of gas for a subsequent part. The gas pin may also be 
adjustable such that the direction of the flow of gas from the outlet may 
be quickly and easily oriented. Further, the gas nozzle of the present 
invention facilitates interchangeable gas pins providing another dimension 
of flexibility for the mold designer. 
One advantage of the present invention is that a stationary gas pin for a 
gas assisted injection molding system is provided which includes no moving 
parts and does not require any expensive seals. Another advantage of the 
present invention is that the outlet for the gas does not become clogged 
with resin during successive molding processes. Still another advantage of 
the present invention is that the outlet for the gas is formed by a 
plurality of very small rectangular apertures arranged in a predetermined 
manner such that they approximate the flow path of a hole having a 
diameter of between 0.055 to 0.125 inches. Still another advantage of the 
present invention is that the gas nozzle may be mounted in the cavity of 
the mold such that it is very accessible to the operator and may be 
quickly and easily adjusted, removed, changed or cleaned without 
complicated maintenance or extended shut down time. 
Other features and advantages of the present invention will be readily 
appreciated as the same becomes better understood after reading the 
subsequent description when considered in connection with the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
Referring now to the drawings, a gas assisted plastic injection molding 
apparatus is generally shown at 10 in FIGS. 1 through 3. The gas assisted 
plastic injection molding apparatus includes a plastic injector 12 which 
may have a screw-type ram 14 which is operatively controlled by a plastic 
injection control mechanisms 16. The plastic injection control mechanism 
16 may comprise, for example, an electrical motor or hydraulic pump which 
drives the screw ram 14 and/or a gate valve to move molten resin 18 from a 
passage 20 in the injector 12 through an injector nozzle 22. 
Alternatively, the screw ram 14 may be replaced by any suitable means for 
forcing a shot of resin 18 from the injector 12 and into a mold, generally 
indicated at 24. 
A sprue 26 is located between the injector nozzle 22 and a runner 28 in the 
mold 24. Similarly, a mold gate 30 is located between the runner 28 and 
the cavity 32 of the mold 24. The cavity 32 is defined by a cavity surface 
34 which, in turn, defines the shape of the plastic article which is 
formed thereby. 
A pressurized gas mechanism is generally indicated at 36 and includes a 
source of pressurized gas 38 and a pressure regulator 40. A gas nozzle, 
generally indicated at 42 in FIGS. 1 through 3, is employed to inject 
pressurized gas into the mold 24. More specifically, the gas nozzle 42 may 
be located in the runner 28 of the mold as shown in FIG. 1. Note here that 
the plastic resin 18 is shown just prior to injection into the mold. 
Alternatively, the gas nozzle 42 may also be located in the mold cavity 32 
as shown in FIG. 2. As illustrated in this Figure, the plastic resin 18 
has partially filled the mold cavity 32 and the plastic injection is about 
to cease. Further, and as shown in FIG. 3, a plastic article as defined by 
the cavity 32 of the mold 24 has been fully formed in response to the 
plastic injection and the introduction of pressurized gas through the gas 
nozzle 42 located in the cavity 32. 
The plastic injection molding apparatus 10 further includes a flow front 
sensor control system, generally indicated at 43. This sensor control 
system 43 includes sensors 44 located at one or more predetermined 
locations at the cavity surface 34. A programmable data processing unit, 
or controller, 46 is employed to receive and store data from one or more 
of the sensors 44. The controller 46 also processes the data and thereupon 
selectively sends signals to the gas assisted plastic injection control 
mechanism 16 as well as the pressurized gas mechanism 36. These signals 
include a "stop injection" signal and a "start gas" signal. In this way, 
the gas assisted plastic injection molding apparatus 10 causes the plastic 
injection to start and stop and also causes the introduction of 
pressurized gas into the cavity to start and stop in response to those 
signals. The operation of the flow front sensor control system 43 is fully 
described in my previously identified U.S. Pat. No. 5,639,405. 
Referring now to FIG. 4, the gas nozzle 42 is shown mounted to the mold 24. 
Depending on the preference of the designer, part geometry and other 
considerations, the nozzle 42 may be mounted so as to inject gas into the 
runner 28 as illustrated in FIG. 1 or into the mold cavity 32 as 
illustrated in FIGS. 2 and 3. In either case, the mold 24 will include a 
threaded port 48 which is drilled through the mold and tapped. The 
threaded port 48 is in fluid communication with the source of pressurized 
gas 38 through a conduit 50 or any other suitable means. 
As best shown in FIGS. 4 through 6, the gas nozzle 42 may be a unitary 
steel member including a body 52 having an inlet 56 in fluid communication 
with the source of pressurized gas 38. The gas nozzle 42 also includes an 
outlet, generally indicated at 58, through which the gas leaves the nozzle 
42. In addition, the nozzle 42 includes a passage 57 which extends between 
the inlet 56 and the outlet 58. More specifically, the body 52 includes a 
threaded portion 60 which is threadably received in the port 48 such that 
the gas nozzle 42 is mounted in fluid communication with the source of 
pressurized gas 38 from the runner 28 or cavity 32 side of the mold 24. In 
this way, the nozzle 42 may be quickly replaced or serviced without having 
to remove the mold 24 from the platen (not shown). The body 52 also 
includes a pin portion 62 which defines an outer surface 64 and a terminal 
end 66. As illustrated in the figures, the terminal end 66 may be recessed 
into the bore of the pin portion 62. The pin portion 62 is cylindrical in 
shape such that the outer surface 64 is arcuate. In addition, the body 52 
includes a barrel portion 68 which is located between the threaded portion 
60 and the pin portion 62 such that the threaded and pin portions 60, 62 
extend from the barrel portion 68 on opposite sides thereof. 
The barrel portion 68 is cylindrical in shape and defines a pair of annular 
shoulders 70, 72 located at either end of the cylindrical barrel portion 
68. The barrel portion 68 also includes an annular groove 74 which is 
disposed between the pair of annular shoulders 70, 72. A sealing member 76 
is received in the annular groove 74 of the barrel portion 68 for 
providing a seal between the body 52 and the port 48 in the mold structure 
24. The sealing member 76 may be an annular neoprene gasket or any other 
suitable sealing member. 
Typically, shoulders 70 of the barrel portion 68 will be disposed flush 
with the surface of the runner 28 or the cavity surface 34 in the mold 24. 
On the other hand, the body 52 is threaded into the port 48 until shoulder 
72 comes into abutting contact with the stop surface 78 formed at a point 
in the port 48 where the diameter thereof changes to accommodate the 
barrel portion 68 which has a larger diameter than either the threaded 
portion 60 or the pin portion 62 of the body 52. 
As shown in the Figures, the pin portion 62 extends into either the runner 
28 or the cavity 32 of the mold 24. In one embodiment shown in FIGS. 5 
through 7, the outlet 58 includes a plurality of apertures 80 arranged in 
a predetermined manner relative to one another such that a line connecting 
at least three of the plurality of apertures 80 approximates the sides of 
a right triangle. Stated another way, the apertures 80 are arranged 
relative to one another such that the spacing between at least three 
apertures can be defined by the relationship X.sup.2 +Y.sup.2 =Z.sup.2, 
where X is the distance between the first and second apertures, Y is the 
distance between the second and third aperture and Z forms the hypotenuse 
of the right triangle and is the distance between the first and third 
aperture. Furthermore, the apertures 80 are spaced from any adjacent 
aperture 80 in the outlet 58 in a range between 0.015 and 0.050 inches. 
The diameters of the apertures 80 may be in the range between 0.0025 and 
0.006 inches. 
As shown in FIGS. 5 and 7, the outlet 58 may be located in the terminal end 
66 of the pin portion 62. On the other hand, the outlet 58 may be located 
on the arcuate outer surface 64 of the pin portion 62. It will be 
appreciated that when the apertures 80 are located on the arcuate outer 
surface 64, the arrangement of the apertures 80 will only approximate a 
right triangle due to the curvature of this surface. It should also be 
noted that the outlet 58 may also be located on both the terminal end 66 
and the outer surface 64 of the pin portion 62. 
Another embodiment of the present invention is shown in FIGS. 8 and 9, 
wherein like numerals are used to indicate like parts. The outlet 58 may 
include a plurality of apertures 80 arranged in a predetermined radial 
manner about a common centerpoint on the outlet 58. More specifically, the 
plurality of apertures 80 are disposed in a prearranged series of 
concentric circles about a common centerpoint on either the terminal end 
66 or on the arcuate outer surface 64 of the pin portion 62. As with the 
apertures 80 illustrated in FIGS. 5-7, the apertures 80 of the outlet 
illustrated in FIGS. 8 and 9 are spaced from adjacent apertures 80 in a 
range between 0.015 and 0.050 inches. Furthermore, the diameter of the 
apertures 80 is in the range between 0.0025 and 0.006 inches. 
Yet another embodiment of the present invention is shown in FIG. 10 wherein 
like numerals are used to indicate like parts. In this figure, the outlet 
58 includes a plurality of apertures 80 arranged in a predetermined manner 
relative to one another such that a line connecting at least three of the 
plurality of apertures 80 approximates the size of an equilateral 
triangle. Stated another way, the apertures 80 are arranged relative to 
one another such that the spacing between at least three apertures can be 
defined by the relationship X=Y=Z, where X is the distance between the 
first and second apertures, Y is the distance between the second and third 
apertures and Z forms the third side of an equilateral triangle and is 
equal to the distance between the first and third apertures. As in the 
other embodiments, the apertures 80 are spaced from any adjacent aperture 
80 in the outlet 58 in a range between 0.015 and 0.050 inches. The 
diameters of the apertures 80 may be in the range between 0.0025 and 0.006 
inches. 
Referring now to FIGS. 11 through 17 where like numerals are used to 
designate like parts, another embodiment of the present invention is 
illustrated. More specifically and referring to FIGS. 11 through 13, the 
outlet 58 may include a plurality of apertures 81 wherein at least some of 
the apertures 81 have a rectangular shaped arranged such that the 
longitudinal axis of consecutive rectangular shaped apertures 81 are 
parallel to one another. As shown in FIGS. 11 through 12, the outlet 58 
may be located on either the terminal end 66 or the outer surface 64 of 
the pin portion 62. Alternatively, it will be appreciated that the outlet 
58 may be located on both the terminal end 66 and the outer surface 64 of 
the pin portion 62. 
Furthermore, the width of the rectangular shaped apertures 81 is preferably 
within the range between approximately 0.002 and 0.006 inches. The length 
of the rectangular shaped apertures 81 along their longitudinal axis is 
preferably greater than 0.014 and less than 1.0 inches. Additionally, the 
rectangular shaped apertures 81 are spaced from any adjacent aperture in 
the outlet 58 in the range between 0.010 and 0.050 inches. 
Referring now to FIG. 14, the outlet 58 may also include a plurality of 
apertures wherein at least some of these apertures 81 have a rectangular 
shape arranged in such a way that the apertures 81 approximate a radial 
pattern about a common centerpoint and such that the longitudinal axis of 
the radially spaced rectangular shaped apertures 81 are parallel to one 
another. As with the other embodiments discussed above, the outlet 58 
shown in FIG. 14 may be located on either the terminal end 66 or outer 
surface 64 of the pin portion 62. Additionally, the outlet 58 may be 
located on both the terminal end 66 and the outer surface 64 of the pin 
portion 62. The size and spacing of the rectangular shaped apertures 81 
shown in FIG. 14 may be the same as those shown and described in 
connection with FIGS. 11 through 13. 
Alternatively, and as shown in FIG. 15, the plurality of apertures may 
include both rectangular shaped apertures 81 and non-rectangular apertures 
80. The non-rectangular shaped apertures 80 may be of any other geometric 
shape. Furthermore, and throughout the embodiments shown in FIGS. 11 
through 15, it will be appreciated with reference to FIGS. 16 and 17 that 
the plurality of apertures 80, 81 may be arranged relative to one another 
such that three lines drawn between three points on at least two apertures 
80, 81 form a right triangle generally indicated at 83. Alternatively, the 
plurality of apertures 80, 81 may be arranged relative to one another such 
that three lines drawn between three points on at least two apertures 80, 
81 form an equilateral triangle generally indicated at 85. 
Another embodiment of the present invention is illustrated in FIGS. 18 
through 20 which shows a gas nozzle assembly 42'. As with the gas nozzle 
42 illustrated in FIGS. 5 through 10 and depending on the preference of 
the designer, part geometry and other considerations, the gas nozzle 
assembly 42' may be mounted so as to inject gas into the runner 28 as 
illustrated in FIG. 1 or into the mold cavity 32 as illustrated in FIGS. 2 
and 3. In either case, the mold 24 or runner 28 will include a threaded 
port 48 which is drilled through the mold or runner and tapped. The 
threaded port 48 is in fluid communication with a source of pressurized 
gas 38 through a conduit 50 or any other suitable means. 
Referring now to FIGS. 18 through 20, where like numerals are used to 
designate like structures throughout the figures and where some numeral 
are primed, the gas nozzle assembly 42' includes a fitting, generally 
indicated at 82, having an inlet 56 providing fluid communication with the 
source of pressurized gas 38. The gas nozzle assembly 42' also includes a 
gas pin portion, generally indicated at 62, having an outlet, generally 
indicated at 58, through which gas leaves the nozzle assembly 42'. A 
passage, generally indicated at 57, extends between the inlet 56 and the 
outlet 58 through the gas pin portion 62 and the fitting 82. The fitting 
82 includes a body 52 having a first threaded portion 60 for mounting the 
fitting in fluid communication with a source of pressurized gas 38 and a 
second threaded portion 84. A barrel 68 is located between the first 
threaded portion 60 and the second threaded portion 84 such that the first 
and second threaded portions 60, 84 extend from the barrel portion 68 on 
opposite sides thereof. 
The barrel portion 68 is cylindrical in shape and defines a pair of annular 
shoulders 86, 88, located at either end of the cylindrical barrel portion 
68. A pair of gaskets 90 abut the annular shoulders 86, 88 of the barrel 
portion 68 for, among other reasons, providing a seal between the fitting 
82 and the port 48 in the mold structure 24. The gaskets 90 may be an 
annular neoprene gasket or any other suitable sealing member. The barrel 
portion 68 has a larger diameter than either the first or second threaded 
portions 60, 84. The body 52 of the fitting 82 is threaded into the port 
48 until the gasket 90 is compressed between the barrel 68 and the stop 
surface 78 formed at a point in the port 48 where the diameter thereof 
changes to accommodate the barrel portion 68. This is similar to the 
structure illustrated in FIG. 4. 
The second threaded portion 84 on the fitting 82 includes an opening 92 
defining seat 94. The gas pin portion 62 includes a head 96 received in 
the opening 92. The gas pin portion 62 also includes a ferrule 98 which 
cooperates with the seat 94 and an elongated shaft portion 100 extending 
therefrom. The shaft portion 100 includes a terminal end 102. An end 
flange 104 is carried on the shaft portion 100 adjacent the back of the 
ferrule 98 for a purpose which will be described in greater detail below. 
In the embodiment disclosed in these figures, the ferrule 98 and end 
flange 104 are formed separately from the shaft portion 100 but those of 
ordinary skill in the art will appreciate that all of these components may 
be formed integrally or separate from one another. 
As previously illustrated in FIGS. 1 through 2, the pin portion 62 extends 
into either the runner 28 or the cavity 32 of the mold 24. The outlet 58 
includes a plurality of apertures 80 or 81 arranged in a predetermined 
manner relative to one another. The outlet 58 may be located on the 
terminal end 102 of the shaft portion 100. Alternatively, the outlet 58 
may be located on the outer arcuate surface of the shaft portion 100. In 
addition, it is possible that the outlet 58 may be located on the terminal 
end 102 as well as the outer arcuate surface of the shaft portion 100. As 
illustrated in FIGS. 18 through 20, the apertures 80 are located on the 
outer arcuate surface of the shaft portion 100 and arranged in a radial 
manner about a center point. However, it will be appreciated that the 
apertures may be arranged so as to form right triangles or equilateral 
triangles. Furthermore, the apertures may be rectangular or 
non-rectangular in shape as described and shown above, or may be any other 
geometric shape. In the embodiment illustrated in FIGS. 18 through 20, 
each of the apertures 80 or 81 may be spaced from any adjacent aperture 80 
or 81 in the outlet 58 in a range between 0.010 and 0.050 inches. 
The gas pin portion 62 of the gas nozzle assembly 42' is adjustably and 
removably mounted to the fitting 82 such that the orientation of the 
outlet 58 relative to a mold 24 or runner 28 may be changed. More 
specifically, the gas nozzle assembly 42' further includes a retainer 106 
received on the second threaded portion 84 to adjustably and removably 
mount the gas pin portion 62 in fluid communication with the fitting 82. 
The retainer is a cap 106 having an aperture 108 through which the shaft 
portion 100 of the gas pin portion 62 extends. The cap 106 is threadingly 
received on the second portion 84 of the fitting 82 such that the position 
of the gas pin portion 62 relative to the fitting 82 may be adjusted by 
loosening the cap 106 relative to the second threaded portion 84. To that 
end, the cap 106 may include tabs 110 which are adapted for use with 
certain tools or a hex head 112. Both structures, or any other structure 
suitable for the purpose of loosening or tightening the cap, may be 
employed. The cap 106 abuts the gasket 90 on one side of the barrel 68 and 
holds the end flange 104, ferrule 98 and head 96 in compression relative 
to the opening 92 and the seat 94 in the second threaded portion 84. The 
gas nozzle assembly 42' of the present invention facilitates the easy 
adjustment and/or removal of the gas pin portion 62. More specifically, 
the outlet 58 of the gas pin portion 62 may be adjusted so as to direct 
the apertures 80, 81 in any way such that the gas flowing from the pin may 
be directed where desired. Additionally, shorter or longer pin portions 62 
may be quickly and easily substituted as desired thus providing another 
dimension of flexibility for the mold designer. 
The apertures 80, 81 are cut into the steel of the pin portion 62 using a 
laser and are very small as noted above. Yet due, in part, to the number 
of apertures and the physical arrangement relative to one another, the gas 
flow through the outlet 58 approximates the flow through a 1/8 inch hole. 
This provides excellent flow characteristics for the gas nozzle 42 and gas 
nozzle assembly 42' of the present invention without the problem of having 
the apertures 80, 81 becoming clogged by molten resin. More specifically, 
while a skin of molten resin may form over the outlet 58 at the completion 
of a molding cycle, the individual apertures 80, 81 are sufficiently small 
such that they do not become clogged. The "skin" covering the plurality of 
apertures 80, 81 is then easily blown off during the next injection of gas 
for a subsequent part. 
The present invention has been described in an illustrative manner. It is 
to be understood that the terminology which has been used is intended to 
be in the nature of words of description rather than of limitation. 
Many modifications and variations of the present invention are possible in 
light of the above teachings. Therefore, within the scope of the appended 
claims, the present invention may be practiced otherwise than as 
specifically described.