Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR PROPORTIONALLY CONTROLLING FLUID
DELIVERY TO A MOLD
BACKGROUND OF THE INVENTION
The present invention relates to automatic control of plastic flow though
injection
nozzles in a molding machine. More particularly the invention relates to
proportional
control of plastic flow via proportional control of the actuator mechanism for
a valve for a
nozzle particularly where two or more nozzles are mounted on a hotrunner for
injection
into one or more mold cavities. The proportional control is achieved via the
use of one or
more sensors which senses a selected condition of the plastic flow through a
manifold,
nozzle or into a mold and the use of the recorded condition in conjunction
with a selected
nozzle design, hotrunner/manifold design, actuator design, actuator drive
mechanism and
/or flow control mechanism. Proportional control of melt flow typically refers
to control of
the rate of melt flow according to an algorithm utilizing defined by a sensed
condition as a
variable.
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SUMMARY OF THE INVENTION
In accordance with the invention there is provided an apparatus and method for
proportionally controlling the rate of melt flow through a melt flow path in
an injection
molding machine, in particular controlling the melt flow through two nozzles.
More particularly, there is provided in an injection molding machine having
first
and second nozzles for delivering melt material from a common manifold to one
or more
mold cavities, an apparatus for controlling delivery of the melt material from
the nozzles to
the one or more mold cavities, each nozzle having an exit aperture
communicating with a
gate of a cavity of a mold and being associated with an actuator
interconnected to a melt
flow controller, the apparatus comprising :
a sensor for sensing a selected condition of the melt material through at
least one of
the nozzles ; and,
an actuator controller interconnected to each actuator, each actuator
controller
comprising a computer interconnected to a sensor for receiving a signal
representative of
the selected condition sensed by the sensor, the computer including an
algorithm utilizing a
value corresponding to a signal received from the sensor as a variable for
controlling
operation of an actuator for the at least one nozzle.
At least one of the nozzles has a seal surface disposed on a tip end of the
nozzle
which is engaged and in compressed contact with a complementary surface
surrounding the
gate of a cavity of a mold, the engaged surfaces forming a seal against
leakage of the melt
material around the nozzle and maintaining the pressure of the melt against
loss of pressure
due to leakage. The at least one nozzle is expandable upon heating to a
predetermined
operating temperature, the nozzle being mounted relative to the surface
surrounding the
gate such that the seal surface disposed on the tip end of the nozzle is moved
into
compressed contact with the complementary
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surface surrounding the gate upon heating of the nozzle to the predetermined
operating
temperature. The complementary mating surfaces of the nozzle and the gate area
of the
mold are typically radially disposed relative to the axis of the exit aperture
of the nozzle,
although the mating surfaces may also be disposed longitudinally or axially.
The tip end of the nozzle may comprise a single unitary piece or, in another
embodiment, an outer unitary piece formed of a first material and an inner
unitary piece
formed of a second material, the first material being substantially less heat
conductive
than the second material. The complementary mating surfaces of the nozzle and
the gate
area of the mold are typically radially disposed relative to the axis of the
exit aperture of
to the nozzle, although the mating surfaces may also be disposed
longitudinally or axially.
At least one of the nozzles may have a tip end having a central portion having
a
central bore in alignment with a gate and an outer circumferential flange
portion
surrounding the gate and the central portion of the tip end of the at least
one nozzle.
The melt flow controller of the apparatus typically comprises a pin which is
controllably slidable via interconnection to an actuator along a reciprocal
path of
movement within the bore of a nozzle, or the controller typically comprises a
rotary
valve having a rotatable flow channel connecting an input flow channel to the
exit
aperture of at least one of the nozzles, the rotatable channel being
interconnected to the
actuator and controllably rotatable via the actuator to selectively vary the
rate of flow of
plastic melt through the rotatable flow channel to the exit aperture according
to the
degree of rotation of the rotary valve. The rotary valve typically comprises a
cylinder
rotatably mounted within a housing the cylinder having a bore rotatably
communicable
with a pair of bores in the housing.
One or more actuators may comprise a piston mounted within a fluid sealed
housing, the piston having a stem extending outside the fluid sealed housing,
the valve
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pin having a head wherein the stem is readily detachably interconnected to the
head of
the valve pin outside the fluid sealed housing.
One or more actuators may comprise an electrically driven motor, the motor
being mechanically interconnected to either a valve pin disposed in a bore of
one of the
nozzles such that the valve pin is reciprocally drivable within the bore of
the nozzle by
the motor, or a rotary valve for rotatable drive of a rotatable component
having a fluid
flow bore, the motor being electrically interconnected to the algorithm, the
algorithm
controlling the drive of the motor.
Each actuator for each of the first and second nozzles may be fluid driven
)0 wherein each actuator is commonly supplied with an actuator drive fluid
flowing through
a manifold which commonly delivers fluid to each of the nozzles.
The actuator controller for a fluid driven actuator typically comprises a
solenoid
having a piston controllably movable between selected positions for
selectively
delivering a pressurized actuator drive fluid to one or the other of at least
two chambers
of the actuator.
The actuator controller for a fluid driven actuator may include a drive fluid
valve
which receives pressurized drive fluid from a source, the drive fluid valve
having one or
more fluid ports sealably communicating with one or more complementary fluid
drive
chambers disposed within the fluid driven actuator, the drive fluid valve
being
controllably driven to selectively distribute received pressurized fluid
through the one or
more fluid ports to the one or more complementary fluid drive chambers of the
actuator.
The drive fluid valve typically comprises a sealed housing and a plunger
movable within
the sealed housing to positions along a path wherein the one or more fluid
ports are open
to communication, partially open to communication, or closed from
communication with
the one or complementary fluid drive chambers by the plunger, the plunger
being
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controllably movable to any position along the path between the open and
closed
positions such that flow of the drive fluid to a drive fluid chamber is
controllably
variable to a selected rate. The plunger typically comprises a slidably
movable rod
having interference projections which are selectively slidable by movement of
the rod
over the fluid ports to open, partially open to any desired degree, or close
the fluid ports.
In another embodiment, at least one gate of a mold may be an edge gate
extending radially outward through a mold cavity plate, at least one of the
nozzles having
a bore having a first portion having an inlet for the plastic melt which is
not in alignment
with the edge gate and a second portion extending radially outward from the
first portion
terminating in the exit aperture being in alignment with the edge gate. In
such an
embodiment the nozzle may have an exit end comprising a center nozzle member
and a
circumferential nozzle member surrounding the center nozzle member, the exit
aperture
extending through the center nozzle member in alignment with one of the gates,
the
circumferential nozzle member surrounding the one gate, wherein a groove is
formed
between the circumferential nozzle member and the center portion.
The apparatus typically includes a plurality of enclosed heat conductive tubes
containing a fluid which vaporizes and condenses within each tube and a wick
disposed
within and along the length of each tube, at least one of the manifold and one
of the
nozzles having the tubes embedded within the manifold or the nozzle making
heat
conductive contact with the manifold or the nozzle.
The apparatus may include a melt flow reservoir sealably communicating with
and disposed between a common feed channel of the manifold and an exit
aperture of a
nozzle, the reservoir having a defined volume sealably fillable and closed off
from
communication with the common feed channel, the reservoir including an
injection
mechanism operable on melt material residing in the reservoir to force the
melt material
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through the exit aperture of the nozzle under pressure. In such an embodiment,
the melt
flow controller preferably comprises a valve disposed in the melt flow between
the
reservoir and the exit aperture of the nozzle. The melt flow controller may
also
alternatively comprise the injection mechanism.
The sensor typically comprises a pressure transducer interconnected to at
least
one of the bore of a nozzle or a mold cavity for detecting the pressure of the
melt
material. The sensor may comprise a mechanism selected from the group
consisting of a
pressure transducer, a load cell, a valve pin position sensor, a temperature
sensor and a
barrel screw position sensor.
In a typical embodiment, at least one of the nozzles has a bore, a valve pin
as the
flow controller and a surface for forming a gap with a surface of the bore
away from the
gate, wherein the size of the gap is increased when the valve pin is retracted
away from
the gate and decreased when the valve pin is displaced toward the gate.
Alternatively the
valve pin and the bore may be configured such that valve pin has a surface for
forming a
gap with a surface of the bore away from the gate, wherein the size of the gap
is
decreased when the valve pin is retracted away from the gate and increased
when the
valve pin is displaced toward the gate. In such embodiments the apparatus
typically
includes a plug mounted in a recess of the manifold opposite a side of the
manifold
where the at least one nozzle is coupled, the plug having a bore through which
a stem of
the valve pin of the nozzle passes, the valve pin having a head which has the
surface
which forms the gap with the complementary surface of the bore, the bore of
the plug
through which the stem passes having a smaller diameter than the valve pin
head at the
valve pin head's largest cross-sectional point and the recess of the manifold
having a
larger diameter than the diameter of the valve pin head at the valve pin
head's largest
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point, so that the valve pin can be removed from the manifold from a side of
the manifold.
in which the recess is formed when the plug is removed from the manifold.
The apparatus most preferably includes a second-sensor for sensing a second
selected condition of the melt material through the second nozzle, the
computer being
interconnected to the second sensor for receiving a signal representative of
the selected
condition sensed by the second sensor, the computer including an algorithm
utilizing a
value corresponding to a signal received from the second sensor as a variable
for
controlling operation of an actuator for the second nozzle.
The present invention also provides an injection molding machine having first
and
second nozzles for delivering melt material from a common manifold to one or
more mold
cavities, apparatus for controlling delivery of the melt material from the
nozzles to the one
or more mold cavities, each nozzle having an exit aperture communicating with
a gate of a
cavity of a mold and being associated with an actuator interconnected to a
melt flow
controller, the apparatus comprising:
a sensor for sensing a selected condition of the melt material through at
least one of
the nozzles;
an actuator controller interconnected to each actuator, each actuator
controller
comprising a computer interconnected to a sensor for receiving a signal
representative of
the selected condition sensed by the sensor, the computer including an
algorithm utilizing a
value corresponding to a signal received from the sensor as a variable for
controlling
operation of an actuator for the at least one nozzle;
wherein at least one of the nozzles has a tip end having a central portion
having a
central bore in alignment with the gate and an outer circumferential flange
portion
surrounding the gate and the central portion of the tip end of the at least
one nozzle.
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Brief Description of the Drawings
Figure 1 is a partially schematic cross-sectional view of an injection molding
system
according to one embodiment of the present invention ;
Figure 2 is an .enlarged fragmentary cross-sectional view of one side of the
injection
molding system of Figure 1;
Figure 3 is an enlarged fragmentary cross-sectional view of an alternative
embodiment of a system similar to Figure 1, in which a plug is used for easy
removal of the
valve pin ;
Figure 4 is an enlarged fragmentary cross-sectional view of an alternative
embodiment of a system similar to Figure 1, in which a threaded nozzle is
used;
Figure 5 is a view similar to Figure 4, showing an alternative embodiment in
which
a plug is used for easy removal of the valve pin ;
Figure 5a is a generic view of the end of the nozzles shown in Figs 1-5;
Figure 5b is a close-up more detailed view of a portion of the nozzle end
encircled
by arrows 5b-5b shown in Fig. 5a;
Figure 5c is cross sectional view of an alternative nozzle end configuration
similar
to the Figs. 5a and 5b configuration;
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Figure 6 shows a fragmentarycress-sectional view of a-system similar to-Figure
1. showing an altematiue .embodiment in which a forward valve pin shut-off is
used;
Figure 7 shvwsan enlarged fragmentary view of the embodiment of Figure-6,
showing the valve pin'inTthe open-and closed positions, respectively;
s Figure 8is a cross-sertinnat view of anaternative-embndimenrofthe }resent
invention similar-to Figure 6, in which a threaded nozzle is used with a plug
for easy
removal.. olthe.valve piny
Figure-9-is an-enlarged-fragmentary view-of the- embodiment o-fFigure-8-, iir
which the valve pin is shown in the open andclosed positions;
Figure ifl-h -an enlarged view of an alternative embodiment tsfthe valve pin,
shown-in-tlie elesedd position-;
Figure 11 is a fragmentary crass section] view of an alternative embodiment of
an injection molding system having flow control that includes a valve pin that
extends to
the gateT and..
rs Figtrre-12 is an- enlarged fragmentary cross-sectiena} detail-of the-flow
conval
area.;
Figure 13 is a side cross-section of The lower end of another nozzle having~a
std valve pin;.
Figure t3 a isa~iew al~g lines l3a-r3 a ofgig. l3;
Figure 1-4 is e.schematic side. -cross-sectional view of a sensor monitored
injection
molding system havingrotary-va1ves- disposed in the.manifo1d.flow channels nr_
c olling melt-flow inte- a mold-eat;
Figure 15 is a tap plan cross sectional view of one.of rotary valves of Figure
1-
along lines 15-15 showing -the Totary valve in a shut-off position;
21 Figure L6.is a side c~rnss=sertionR1_view alone of therntary.valves
ofFignre 14; .
RECTIFIED SHEET (RULE 91) ISA/EP
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Figure 17 is top view of one of the rotary valves of Figure 14 showing limit
stops
for limiting the rotation of the rotary cylinder of the rotary valves;
Figure 18 is a top view of one of the drive actuator-controllers of Figure 14
showing the position of bolts for connecting the drive-actuator relative to
the valve;
Figure 19 is a schematic side cross-sectional view of an alternative rotary
valve
flow controlled system showing a dual drive actuator which simultaneously
drives/controls a rotary valve and a valve pin which is additionally used in
the bore of
one of the down bores feeding into the cavity of the mold;
Figure 20 is a more detailed view of the mechanical interconnection between
the
dual drive actuator of Figure 19 and the rotary valve and the valve pin;
Figure 21 is a schematic top view of a drive wheel component of the drive
actuator of Figure 19 showing the gear mesh relationship between the drive
wheel and
the follower wheel of the rotary valve;
Figure 22 is a side cross-sectional view of a shaftless motor for use as an
alternative actuator for a valve or other flow control mechanism in accordance
with the
invention, the motor having an axially movable screw for driving the flow
controller;
Figure 23 is a side cross sectional view of a sensor monitored nozzle having a
straight valve pin interconnected to a readily detachable actuator having a
readily
attachable and detachable valve pin, the actuator being fed with pressurized
drive fluid
by a manifold which commonly feeds pressurized drive fluid to a plurality of
actuators;
Figure 24 is an exploded view of the actuator interconnection components to
the
manifold shown in Fig. 23;
Figure 25 is an exploded view of the actuator interconnection to the drive
fluid
manifold of Fig. 23;
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Figure 26 is an isometric view of a modular embodiment of a pressurized drive
fluid manifold showing a modular configuration for the manifold;
Figure 27 is an isometric close-up view of a modular arm and actuator
interconnection according to the Fig. 26 embodiment showing the alignment of a
modular manifold with the fluid input/output ports of the actuator;
Figure 28 is a schematic side cross-sectional view of a sensor monitored valve
gated nozzle having an actuator fed by a drive fluid delivery manifold and a
proportional
valve mounted on the manifold above the valve for precisely controlling the
delivery of
drive fluid to the individual actuator from the manifold;
Figure 29 is a side cross-sectional view of an embodiment having an Edge-Gated
nozzle tip having sensor feedback control loop control over the actuator;
Figure 30 is a more detailed close-up view of the interface between the edge
gated nozzle tip of Fig. 29 and the gate area of a mold cavity;
Figure 31 is a side cross-sectional view of an embodiment of the invention
having
a defined volume reservoir disposed in the melt flow channel leading from the
main
injection screw to the output of an injection nozzle.
Detailed Description
Figures 1-2 show one embodiment of an injection molding system according to
the present invention having two nozzles 21, 23 the plastic flow through which
are to be
controlled dynamically according to an algorithm as described below. Although
only
two nozzles are shown in Figs. 1-2, the invention contemplates simultaneously
controlling the material flow through at least two and also through a
plurality of more
than two nozzles. In the embodiment shown, the injection molding system I is a
multi-
gate single cavity system in which melt material 3 is injected into a cavity 5
from the two
gates 7 and 9. Melt material 3 is injected from an injection molding machine
11 through
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an extended inlet 13 and into a manifold 15. Manifold 15 distributes the melt
through
channels 17 and 19. Although a hot runner system is shown in which plastic
melt is
injected, the invention is applicable to other types of injection systems in
which it is
useful to control The rate at which a material (e.g., metallic or composite
materials) is
delivered to a cavity.
Melt is distributed by the manifold through channels 17 and 19 and into bores
18
and 20 of the two nozzles 21 and 23, respectively. Melt is injected out of
nozzles 21 and
23 and into cavity 5(where the part is formed) which is formed by mold plates
25 and
27. Although a multi-gate single-cavity system is shown, the invention is not
limited to
io this type of system, and is also applicable to, for example, multi-cavity
systems, as
discussed in greater detail below.
The injection nozzles 21 and 23 are received in respective wells 28 and 29
formed in the mold plate 27. The nozzles 21 and 23 are each seated in support
rings 31
and 33. The support rings serve to align the nozzles with the gates 7 and 9
and insulate
the nozzles from the mold. The manifold 15 sits atop the rear end of the
nozzles and
maintains sealing contact with the nozzles via compression forces exerted on
the
assembly by clamps (not shown) of the injection molding machine. An O-ring 36
is
provided to prevent melt leakage between the nozzles and the manifold. A dowel
73
centers the manifold on the mold plate 27. Dowels 32 and 34 prevent the nozzle
23 and
support ring 33, respectively, from rotating with respect to the mold 27.
In the embodiment shown in Figs. 1-3 an electric band heater 35 for heating
the
nozzles is shown. In other embodiments, heat pipes, such as those disclosed in
U.S. Patent
No. 4,389,002, discussed below, may be disposed in a nozzle and used alone or
in
conjunction with a band heater 35. The heater is used to maintain the melt
material at its
processing.
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temperature as far up to the point of exit through./into gates 7 and 9 as
possible. As
shown, the manifold is heated to elevated temperatures sufficient to maintain
the plastic
or other fluid which is injected into the manifold distribution ducts 17, 19
at a preferred
preselected flow and processing temperature. A plurality of heat pipes 4 (only
one of
s which is shown in Figs 2, 3) are preferably disposed throughout the
manifold/hotrunner
15 so as to more uniformly beat and maintain the manifold at the desired
processing
temperature.
The mold plate or body 27 is, on the other hand, typically cooled to a
preselected
temperature and maintained at such cooled temperature relative to the
temperature of the
manifold 15 via'cooling ducts 2 through which water or some other selected
fluid is
pumped during the injection molding process in order to effect the most
efficient
formation of the part within the mold cavity.
As shown in Figs. 1-5b, the. injection nczzle(s) is/are mounted within well 29
so
as to be held in firmly stationary alignment with the gate(s) 7, 9 which lead
into the mold
cavities. The mounting of the heated nozzle(s) is/are arranged so as to
minimize contact
of the nozzle(s) body and its associated components with the cooled mold plate
27 but at
the same time form a seal against fluid leakage back into an insulative air
space in which
the nozzle is disposed thus maintaining the fluid pressure within the flow
bore or channel
against loss of pressure due to leakage. Figs 5a, 5b show a more detailed
schematic view
of the nozzle mountings of Figs. 1-5. As shown, there is preferably provided a
small,
laterally disposed, localized area 39a at the end of the nozzle for making
compressed
contact with a complementary surface 27a of the plate 27. This area of
compressed
contact acts both as a mount for maintaining the nozzle in a stationary,
aligned and
spaced apart from the plate 27 relationship and also as a seal against leakage
of fluid
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back from the gate area into the insulative space in well 29 left between the
nozzle and
the mold
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plate 27. In the embodiment shown the mating area of the nozzle 39a is a
laterally
facing surface although a longitudinally facing surface may also be selected
for effecting
such a seal. The dimensions of the inner and outer pieces are machined so that
compression mating between the laterally facing nozzle surface 39a and plate
surface 27a
occurs upon heating of the nozzle to its operating temperature which expands
both
laterally and longitudinally upon heating. The lateral mating surfaces 27a and
39a
typically enables more ready machining of the parts, although compression
mating
between axially or longitudinally facing surfaces such as 39b and 27b can be
provided
for in the alternative. As shown in Figs 5a, 5b an insulative space 6a is also
left between
the most distal tip end surfaces of the nozzle and the mold such that as
little direct
contact as possible between the heated nozzle and the relatively cooler plate
27 is made.
Another example of lateral surface mating upon heating of the nozzle to
operating
process temperature can be seen in the embodiment shown in Figs 13, 13a. In
this
elastically deformable nozzle which is described in detail in US Patent No.
6261084, inner
nozzle piece 37 is forced downwardly DF, Figs. 13, 13a upon heating of the
apparatus to
operating temperature whereby the undersurface 15a of manifold 15 compresses
downwardly against the upper surface 37a of piece 37 causing the undersurface
of step 37b
to press downwardly DF, Fig. 13a, on the upper surface 39a of piece 39 which
in turn
causes the leg portion 39c, Fig 13a, to pivot P laterally and thus cause
compressed mating
between laterally facing surface 39d and laterally facing surface 27a of mold
27 to occur
thus forming a seal against fluid leakage.
In an alternative embodiment shown in Fig. 5c, the nozzles may be machined or
configured so as to leave a predetermined gap between or a non-compressed
mating
between two axially or longitudinally facing surfaces 27b and 39c (in the
initially
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assembled cold state) which gap will close upon heating the apparatus up to
its operating
plastic processing temperature such that the two surfaces 27b and 39c mate
under
compression to form a seal. As shown in Fig. 5c the insulative air gap 6a is
maintained
along the lateral edges of the outer piece 39 of the nozzle into which plastic
melt does
not flow by virtue of a seal which is formed between the surfaces 27b and 39c
upon
heating of the apparatus up. The same sort of longitudinal/axial seal may be
formed
using another alternative nozzle embodiment such as disclosed in US Patent No.
5,885,628, where the outer nozzle piece forms a flange like member around the
centre
portion of the nozzle. In any case, a relatively small surface on the outside
of the distal
J o tip end of the nozzles makes compression contact with a surface of the
mold plate by
virtue of thermally induced expansion of the nozzles such that a seal against
melt now is
formed.
The nozzles may comprise a single unitary piece or, as shown in the
embodiments in Figs. 1-5b, the nozzles 21 and 23 may comprise two (or more)
separate
unitary pieces such as insert 37 and tip 39. The insert 37 is typically made
of a material
(for example beryllium copper) having a relatively high thermal conductivity
in order to
maintain the melt at its most preferred high processing temperature as far up
to the. gate
as possible by imparting heat to the melt from the heater 35 and/or via heat
pipes as
discussed below. In the embodiments shown, the outer tip piece 39 is used to
form the
seal with the mold plate 27 and preferably comprises a material (for example
titanium
alloy or stainless steel) having a substantially lower thermal conductivity
relative to the
material comprising the inner piece 37 so as reduce/minimize heat transfer
from the
nozzle (and manifold) to the mold as much as possible.
A seal or ring R, Figs. 5a-5c, is provided in the embodiment shown between the
inner 37 and outer 39 pieces. As described in US Patent Nos. 5,554,395 and
5,885,628,
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seal/ring R serves to insulate the two nozzle pieces 37, 39 from each other
minimizing heat
transfer between the two pieces and also by providing an insulative air gap 6b
between the two
nozzle pieces. The R comprises a member made of a metallic alloy or like
material which
may be substantially less heat conductive than the material of which pieces
37, 39 are
comprised. The sealing member R is preferably a thin-walled, substantially
resilient
structure, and may be adapted for engagement by the seal mounting means so as
to be
carried by the nozzle piece 39. The sealing member R extends a preselected
distance
outwardly from the tip portion of the bushing so as to form a sealing
engagement along a
to limited contact area located on the adjoining bore in the mold when the
nozzle.is
operatively disposed therein. More particularly, in one preferred embodiment,
it is
contemplated that the sealing member R will include at least one portion
having a
partially open, generally C-shaped or arc-shaped transverse cross-section.
Accordingly,
the sealing member R may be formed as an O-ring, or as an O-ring defining
spaced,
aligned openings in its surface. Similarly, the sealing member may be formed
as an 0-
ring having an annular portion removed from its inner wall so as to form a C-
shaped or
arc-shaped cross-sectional structure. Further, the sealing member may have a
generally
V-shaped or U-shaped or other cross-section which is dimensionally compatible
with the
mating areas with nozzle pieces 37, 39, if desired. In addition, the sealing
member may
be formed as a flexible length of hollow tubing or a flexible length of
material having the
desired generally C-shaped or arc-shaped or V-shaped or U-shaped transverse
cross-
section. Other possible configurations also will occur to those skilled in the
art in view of
the following detailed description of the present invention.
As shown in Fig 5a, the nozzles may. include one or more heat pipes 4a
embedded within the body of the nozzles for purposes of more efficiently and
uniformly
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maintaining the nozzle at an elevated temperature. In the Fig. 5a embodiment
the heat
pipes 4a are disposed in the nozzle body part 23 which typically comprises a
high
strength tool steel which has a predetermined high heat conductivity and
strength. The
heat pipes 4 mounted in the manifold, Figs. 2,3 and heat pipes 4a, Fig. 5a,
preferably
comprise sealed tubes comprised of copper or steel within which any
vaporizable and
condensable liquid such as water is enclosed. Mercury may be used as the
vaporizable
heat transferring medium in the heat pipes 4, 4a, however, it is more
preferable to use
an inert liquid material such as water. One drawback to the use of water is
that there can
be a tendency for a reaction to occur between the iron in the steel and the
water whereby
the iron combines with the oxygen of the water leaving a residue of hydrogen
which is
an incondensable gas under the conditions of operation of the heat pipe. The
presence of
hydrogen in the heat pipe is deleterious to its effective operation. For the
purposes of
this invention any material, such as iron or an alloy of iron, which tends to
release
hydrogen from water is referred to as "water incompatible material."
1s The use of high strength steel is made practicable by plating or otherwise
covering the interior wall of each heat pipe with a material which is non-
reactive with
water. Examples of such materials are nickel, copper, and alloys of nickel and
copper,
such as monel. Such materials are referred to herein as "water compatible
materials."
The inner wall of each heat pipe 4, 4a is preferably plated with a water
compatible
material, preferably nickel. Such plating is preferably made thick enough to
be
impermeable to water and water vapor. A wick structure 4c is inserted into
each heat
pipe, the wick typically comprising a water compatible cylindrical metal
screen which is
forced into and tightly pressed against the interior wall of a heat pipe. The
wick
preferably comprises a water compatible material such as monel. The elevated
temperature at which the manifold and/or nozzles are maintained during an
injection
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cycle typically ranges between about 200 and about 400 degrees centigrade. The
vapor
pressure of water at these temperatures, although quite high, is readily and
safely
contained with the enclosed tubular heat pipes. In practice, less than the
total volume of
the enclosed heat pipes is filled with the selected fluid, typically less than
about 70% of
such volume, and more typically less than 50%. Following the insertion of the
water, the
outer end of each heat pipe is sealed by conventional means. In a preferred
embodiment
the tubular heat pipes are sealed at one end via a plug as described in US
Patent No.
4,389,002. In operation, the fluid contained within the heat pipes 4, 4a is
vaporized by heat
conduction from the manifold. The fluid vaporizes and travels to each portion
of the heat
pipe from which heat is being extracted and the vapor condenses at each such
portion to
yield up its heat of condensation to maintain the entire length of the heat
pipe at the same
temperature. The vaporization of water from the inner end of the wick
structure 4c creates
a capillary attraction to draw condensed water from the rest of the wick
structure back to
the evaporator portion of the wick thus completing the cycle of water flow to
maintain the
heat pipe action. Where a plurality of heat pipes are disposed around the
nozzle, there is
maintained a uniform temperature around the axis X of the nozzle bores,
particularly in
embodiments where the heat pipes are disposed longitudinally as close to the
exit end of
the nozzle as possible.
In one embodiment, Figs. 1-5, a valve pin 41 having a tapered head 43
controllably engagable with a surface upstream of the exit end of the nozzle
may be used
to control the rate of flow of the melt material to and through the respective
gates 7 and
9. The valve pin reciprocates through the flow channel 100 in the manifold 15.
A valve
pin bushing 44 is provided to prevent melt from leaking along stem 102 of the
valve pin.
The valve pin bushing is held in place by a threadably mounted cap 46. The
valve pin is
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opened at the beginning of the injection cycle and closed at the end of the
cycle. During
the cycle, the valve pin can assume intermediate positions between the fully
open and
closed positions, in order to decrease or increase the rate of flow of the
melt. The head
includes a tapered portion 45 that forms a gap 81 with a surface 47 of the
bore 19 of the
manifold. Increasing or decreasing the size of the gap by displacing the valve
pin
correspondingly increases or decreases the flow of melt material to the gate.
When the
valve pin is closed the tapered portion 45 of the valve pin head contacts and
seals with
the surface 47 of the bore of the manifold.
Figure 2 shows the head of the valve pin in a Phantom dashed line in the
closed
position and a solid line in the fully opened position in which the melt is
permitted to
flow at a maximum rate. To reduce the flow of melt, the pin is retracted away
from the
gate by an actuator 49, to thereby decrease the width of the gap 81 between
the valve pin
and the bore 19 of the manifold.
The actuator 49 (for example, the type disclosed in US Patent No. 5,894,025)
is
mounted in a clamp plate 51 which covers the injection molding system 1. In
the
embodiment shown, the actuator 49 is a hydraulic actuator, however, pneumatic
or
electronic actuators can also be used. Other actuator configurations having
ready
detachability may also be employed such as those described in US Patent No.
5,948,448.
An electronic or electrically powered actuator may also be employed such as
disclosed in
US Patent No. 6,294,122. In the embodiment shown, the actuator 49 includes a
hydraulic
circuit that includes a movable piston 53 in which the valve pin 41 is
threadably mounted
at 55. Thus, as the piston 53 moves, the valve pin 41
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moves with it. The actuator 49 includes hydraulic lines 57 and 59 which are
controlled
by servo valves I and 2. Hydraulic line 57 is energized to move the valve pin
41 toward
the gate to the open position, and hydraulic line 59 is energized to retract
the valve pin
away from the gate toward the close position. An actuator cap 61 limits
longitudinal
movement in the vertical direction of the piston 53. O-rings 63 provide
respective seals
to prevent hydraulic fluid from leaking out of the actuator. The actuator body
65 is
mounted to the manifold via screws 67.
In embodiments where a pneumatically or electrically powered actuator is
employed, suitable pneumatic (air supply) or electrical power inputs to the
actuator are
provided, such inputs being controllable to precisely control the movement of
the
actuator via the same computer generated signals which are output from the
PIDI and
PID2 controllers and the same or similar control algorithm/program used in the
CPU of
FIG. I such that precise control of the movement of the valve pin used to
control plastic
flow is achieved according to the predetermined algorithm selected for the
particular
application.
In the embodiment shown, a pressure transducer 69 is used to sense the
pressure
in the manifold bore 19 downstream of the valve pin head 43. In operation, the
conditions sensed by the pressure transducer 69 associated with each nozzle
are fed back
to a control system that includes controllers PID 1 and PID 2 and a CPU shown
schematically in Figure 1. 'The CPU executes a PID (proportional, integral,
derivative)
algorithm which compares the sensed pressure (at a given time) from the
pressure
transducer to a programmed target pressure (for the given time). The CPU
instructs the
PID controller to adjust the valve pin using the actuator 49 in order to
mirror the target
pressure for that given time. In this way a programmed target pressure profile
for an
injection cycle for a particular part for each gate 7 and 9 can be followed.
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As to each separate nozzle, the target pressure or pressure profile may be
different, particularly where the nozzles are injecting into separate
cavities, and thus
separate algorithms or programs for achieving the target pressures at each
nozzle may be
employed. As can be readily imagined, a single computer or CPU may be used to
execute multiple programs/algorithms for each nozzle or separate computers may
be
utilized. The embodiment shown in Fig. I is shown for purposes of ease of
explanation.
Although in the disclosed embodiment the sensed condition is pressure, other
sensed conditions can be used which relate to melt flow rate. For example, the
position
of the valve pin or the load on the valve pin could be the sensed condition.
If so, a
position sensor or load sensor, respectively, could be used to feed back the
sensed
condition to the PID controller. In the same manner as explained above, the
CPU would
use a PID algorithm to compare the sensed condition to a programmed target
position
profile or load profile for the particular gate to the mold cavity, and adjust
the valve pin
accordingly. Similarly the location of the sensor and the sensed condition may
be other
than in the nozzle itself. The location of the measurement may, for example,
be
somewhere in the cavity of the mold or upstream of the nozzle somewhere in the
manifold flow channel or even further upstream in the melt flow.
Melt flow rate is directly related to the pressure sensed in bore 19. Thus,
using
the controllers PID I and PID 2, the rate at which the melt flows into the
gates 7 and 9
can be adjusted during a given injection molding cycle, according to the
desired pressure
profile. The pressure (and rate of melt flow) is decreased by retracting the
valve pin and
decreasing the width of the gap 81 between the valve pin and the manifold
bore, while
the pressure (and rate of melt flow) is increased by displacing the valve pin
toward the
gate 9, and increasing the width of the gap 81. The PID controllers adjust the
position of
the actuator piston 53 by sending instructions to servo valves 1 and 2.
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By controlling the pressure in a single cavity system (as shown in Figure 1)
it is
possible to adjust the location and shape of the weld line formed when melt
flow 75 from
gate 7 meets melt flow 77 from gate 9 as disclosed in U.S. Patent No.
5,556,582.
However, the invention also is useful in a multi-cavity system. In a multi-
cavity system
the invention can be used to balance fill rates and packing profiles in the
respective
cavities. This is useful, for example, when molding a plurality of like parts
in different
cavities. In such a system, to achieve a uniformity in the parts, the fill
rates and packing
profiles of the cavities should be as close to identical as possible. Using
the same
programmed pressure profile for each nozzle, unpredictable fill rate
variations from
cavity to cavity are overcome, and consistently uniform parts are produced
from each
cavity.
Another advantage of the present invention is seen in a multi-cavity system in
which the nozzles are injecting into cavities which form different sized parts
that require
different fill rates and packing profiles. In this case, different pressure
profiles can be
programmed for each respective controller of each respective cavity. Still
another
advantage is when the size of the cavity is constantly changing, i.e., when
making
different size parts by changing a mold insert in which the part is formed.
Rather than
change the hardware (e.g., the nozzle) involved in order to change the fill
rate and
packing profile for the new part, a new program is chosen by the user
corresponding to
the new part to be formed.
The embodiment of Figures 1 and 2 has the advantage of controlling the rate of
melt flow away from the gate inside manifold 15 rather than at the gates 7 and
9.
Controlling the melt flow away from the gate enables the pressure transducer
to be
located away from the gate (in Figures 1-5). In this way, the pressure
transducer does
not have to be placed inside the mold cavity, and is not susceptible to
pressure spikes
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which can occur when the pressure transducer is located in the mold cavity or
near the
gate. Pressure spikes in the mold cavity result from the valve pin being
closed at the
gate. This pressure spike could cause an unintended response from the control
system,
for example, an opening of the valve pin to reduce the pressure -- when the
valve pin
should be closed.
Avoidance of the effects of a pressure spike resulting from closing the gate
to the
mold makes the control system behave more accurately and predictably.
Controlling
flow away from the gate enables accurate control using only a single sensed
condition
(e.g., pressure) as a variable. The `582 patent disclosed the use of two
sensed conditions
(valve position and pressure) to compensate for an unintended response from
the
pressure spike. Sensing two conditions resulted in a more complex control
algorithm
(which used two variables) and more complicated hardware (pressure and
position
sensors).
Another advantage of controlling the melt flow away from the gate is the use
of a
larger valve pin head 43 than would be used if the valve pin closed at the
gate. A larger
valve pin head can be used because it is disposed in the manifold in which the
melt flow
bore 19 can be made larger to accommodate the larger valve pin head. It is
generally
undesirable to accommodate a large size valve pin head in the gate area within
the end of
the nozzle 23, tip 39 and insert 37. This is because the increased size of the
nozzle, tip
and insert in the gate area could interfere with the construction of the mold,
for example,
the placement of water lines within the mold which are preferably located
close to the
gate. Thus, a larger valve pin head can be accommodated away from the gate.
The use of a larger valve pin head enables the use of a larger surface 45 on
the
valve pin head and a larger surface 47 on the bore to form the control gap 81.
The more
"control" surface (45 and 47) and the longer the "control" gap (81) -- the
more precise
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control of the melt flow rate and pressure can be obtained because the rate of
change of
melt flow per movement of the valve pin is less. In Figures 1-3 the size of
the gap and
the rate of melt flow is adjusted by adjusting the width of the gap, however,
adjusting the
size of the gap and the rate of material flow can also be accomplished by
changing the
length of the gap, i.e., the longer the gap the more flow is restricted. Thus,
changing the
size of the gap and controlling the rate of material flow can be accomplished
by changing
the length or width of the gap.
The valve pin head includes a middle section 83 and a forward cone shaped
section 95 which tapers from the middle section to a point 85. This shape
assists in
facilitating uniform melt flow when the melt flows past the control gap 81.
The shape of
the valve pin also helps eliminates dead spots in the. melt flow downstream of
the gap 81.
Figure 3 shows another aspect in which a plug 87 is inserted in the manifold
15
and held in place by a cap 89. A dowel 86 keeps the plug from rotating in the
recess of
the manifold that the plug is mounted. The plug enables easy removal of the
valve pin
41 without disassembling the manifold, nozzles and mold. When the plug is
removed
from the manifold, the valve pin can be pulled out of the manifold where the
plug was
seated since the diameter of the recess in the manifold that the plug was in
is greater than
the diameter of the valve pin head at its widest point. Thus, the valve pin
can be easily
replaced without significant downtime.
Figures 4 and 5 show additional alternative embodiments of the invention in
which a threaded nozzle style is used instead of a support ring nozzle style.
In the
threaded nozzle style, the nozzle 23 is threaded directly into manifold 15 via
threads 91.
Also, a coil heater 93 is used instead of the band heater shown in Figures 1-
3. The
threaded nozzle style is advantageous in that it permits removal of the
manifold and
nozzles (21 and 23) as a unitary element. There is also less of a possibility
of melt
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leakage where the nozzle is threaded on the manifold. The support ring style
(Figures 1-
3) is advantageous in that one does not need to wait for the manifold to cool
in order to
separate the manifold from the nozzles. Figure 5 also shows the use of the
plug 87 for
convenient removal of valve pin 41.
Figures 6-10 show an alternative embodiment of the invention in which a
"forward" shutoff is used rather than a retracted shutoff as shown in Figures
1-5. In the
embodiment of Figures 6 and 7, the forward cone-shaped tapered portion 95 of
the valve
pin head 43 is used to control the flow of melt with surface 97 of the inner
bore 20 of
nozzle 23. An advantage of this arrangement is that the valve pin stem 1 02
does not
restrict the fldw of melt as in Figures 1-5. As seen in Figures 1-5, the
clearance 81
between the stem 102 and the bore 19 of the manifold is not as great as the
clearance 98
in Figures 6 and 7. The increased clearance 98 in Figures 6-7 results in a
lesser pressure
drop and less shear on the plastic.
In Figures 6 and 7 the control gap 98 is formed by the front cone-shaped
portion
95 and the surface 97 of the bore 20 of the rear end of the nozzle 23. The
pressure
transducer 69 is located downstream of the control gap -- thus, in Figures 6
and 7, the
nozzle is machined to accommodate the pressure transducer as opposed to the
pressure
transducer being mounted in the manifold as in Figures 1-5.
Figure 7 shows the valve pin in solid lines in the open position and Phantom
dashed lines in the closed position. To restrict the melt flow and thereby
reduce the melt
pressure, the valve pin is moved forward from the open position towards
surface 97 of
the bore 20 of the nozzle which reduces the width of the control gap 98. To
increase the
flow of melt the valve pin is retracted to increase the size of the gap 98.
The rear 45 of the valve pin head 43 Temains tapered at an angle from the stem
102 of the valve pin 41. Although the surface 45 performs no sealing function
in this
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embodiment, it is still tapered from the stem to facilitate even melt flow and
reduce dead
spots.
As in Figures 1-5, pressure readings are fed back to the control system (CPU
and
PID controller), which can accordingly adjust the position of the valve pin 41
to follow a
target pressure profile. The forward shut-off arrangement shown in Figures 6
and 7 also
has the advantages of the embodiment shown in Figures 1-5 in that a large
valve pin
head 43 is used to create a long control gap 98 and a large control surface
97. As stated
above, a longer control gap and greater control surface provides more precise
control of
the pressure and melt flow rate.
Figures 8 and 9 show a forward shutoff arrangement similar to Figures 6 and 7,
but instead of shutting off at the rear of the nozzle 23, the shut-off is
located in the
manifold at surface 101. Thus, in the embodiment shown in Figures 8 and 9, a
conventional threaded nozzle 23 may be used with a manifold 15, since the
manifold is
machined to accommodate the pressure transducer 69 as in Figures 1-5. A spacer
88 is
provided to insulate the manifold from the mold. This embodiment also includes
a plug
87 for easy removal of the valve pin head 43.
Figure 10 shows an alternative embodiment of the invention in which a forward
shutoff valve pin head is shown as used in Figures 6-9. However, in this
embodiment,
the forward cone-shaped taper 95 on the valve pin includes a raised section
103 and a
recessed section 104. Ridge 105 shows where the raised portion begins and the
recessed
section ends. Thus, a gap 107 remains between the bore 20 of the nozzle
through which
the melt flows and the surface of the valve pin head when the valve pin is in
the closed
position. Thus, a much smaller surface 109 is used to seal and close the valve
pin. The
gap 107 has the advantage in that it assists opening of the valve pin which is
subjected to
a substantial force F from the melt when the injection machine begins an
injection cycle.
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When injection begins melt will flow into gap 107 and provide a force
component FI
that assists the actuator in retracting and opening the valve pin. Thus, a
smaller actuator,
or the same actuator with less hydraulic pressure applied, can be used because
it does not
need to generate as much force in retracting the valve pin. Further, the
stress forces on
the head of the valve pin are reduced.
Despite the fact that the gap 107 performs no sealing function, its width is
small
enough to act as a control gap when the valve pin is open and correspondingly
adjust the
melt flow pressure with precision as in the embodiments of Figures 1-9.
Figures 11 and 12 show an alternative hot-runner system having flow control in
which the control of melt flow is still away from the gate as in previous
embodiments.
Use of the pressure transducer 69 and PID control system is the same as in
previous
embodiments. In this embodiment, however, the valve pin 41 extends past the
area of
flow control via extension 110 to the gate. The valve pin is shown in solid
lines in the
fully open position and in Phantom dashed lines in the closed position. In
addition to the
1s flow control advantages away from the gate described above, the extended
valve pin has
the advantage of shutting off flow at the gate with a tapered end 112 of the
valve pin 41.
Extending the valve pin to close the gate has several advantages. First, it
shortens injection cycle time. In previous embodiments thermal gating is used.
In
thermal gating, plastication does not begin until the part from the previous
cycle is
ejected from the cavity. This prevents material from exiting the gate when the
part is
being ejected. When using a valve pin, however, plastication can be performed
simultaneously with the opening of the mold when the valve pin is closed, thus
shortening cycle time by beginning plastication sooner. Using a valve pin can
also result
in a smoother gate surface on the part.
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The flow control area is shown enlarged in Figure 12. In solid lines the valve
pin
is shown in the fully open position in which maximum melt flow is permitted.
The valve
pin includes a convex surface 114 that tapers from edge 128 of the stem 102 of
the valve
pin 41 to a throat area 116 of reduced diameter. From throat area 116, the
valve pin
expands in diameter in section 118 to the extension 110 which extends in a
uniform
diameter to the tapered end of the valve pin.
In the flow control area the manifold includes a first section defined by a
surface
120 that tapers to a section of reduced diameter defined by surface 122. From
the section
of reduced diameter the manifold channel then expands in diameter in a section
defined
by surface 124 to an outlet of the manifold 126 that communicates with the
bore of the
nozzle 20. Figures 11 and 12 show the support ring style nozzle similar to
Figures 1-3.
However, other types of nozzles may be used such as, for example, a threaded
nozzle as
shown in Figure 8.
As stated above, the valve pin is shown in the fully opened position in solid
lines.
In Figure 12, flow control is achieved and melt flow reduced by moving the
valve pin 41
forward toward the gate thereby reducing the width of the control gap 98.
Thus, surface
1] 4 approaches surface 120 of the manifold to reduce the width of the control
gap and
reduce the rate of melt flow through the manifold to the gate.
To prevent melt flow from the manifold bore 19, and end the injection cycle,
the
valve pin is moved forward so that edge 128 of the valve pin, i.e., where the
stem 102
meets the beginning of curved surface 114, will move past point 130 which is
the
beginning of surface 122 that defines the section of reduced diameter of the
manifold
bore 19. When edge 128 extends past point 130 of the manifold bore melt flow
is
prevented since the surface of the valve stem 102 seals with surface 122 of
the manifold.
The valve pin is shown in dashed lines where edge 128 is forward enough to
form a seal
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with surface 122. At this position, however, the valve pin is not yet closed
at the gate.
To close the gate the valve pin moves further forward, with the surface of the
stem 102
moving further along, and continuing to seal with, surface 122 of the manifold
until the
end 112 of the valve pin closes with the gate.
In this way, the valve pin does not need to be machined to close the gate and
the
flow bore 19 of the manifold simultaneously, since stem 102 forms a seal with
surface
122 before the gate is closed. Further, because the valve pin is closed after
the seal is
formed in the manifold, the valve pin closure will not create any unwanted
pressure
spikes. Likewise, when the valve pin is opened at the gate, the end 112 of the
valve pin
io will not interfeie'with melt flow, since once the valve pin is retracted
enough to permit
melt flow through gap 98, the valve pin end 112 is a predetermined distance
from the
gate. The valve pin can, for example, travel 6 mm. from the fully open
position to where
a seal is first created between stem 102 and surface 122, and another 6 mm. to
close the
gate. Thus, the valve pin would have 12 mm. of travel, 6 mm. for flow control,
and 6
mm. with the flow prevented to close the gate. Of course, the invention is not
limited to
this range of travel for the valve pin, and other dimensions can be used.
Figs. 13 and 13a show a nozzle having a conventional straight cylindrical pin
41
which may be used as an alternative in conjunction with the automated systems
described above. For example, pressure may be measured in the cavity itself by
a sensor
69a and a program utilized in CPU, Fig. 1 which simply opens, Fig. 13a, and
closes, Fig
13 the exit aperture or gate 9 upon sensing of a certain pressure so as to
create certain
pressure increase in the cavity when closed, or alternatively the tip end of
the pin may be
tapered (tapering shown in dashed lines 41 b) in some fashion so as to vary
the melt flow
rate 20b, in accordance with a predetermined program depending on the sensor
measurement 69a, as the pin 41 is moved into a predetermined closer proximity
to the tip
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end surface 20a of bore 20 (complementary tapering of surface 20a not shown)
in a
similar manner to the way the rate of melt flow may be varied using the
tapered conical
bead 45 of the Figs. 2-5 embodiments.
Figs. 14-21 show an embodiment of the invention using rotary valves 200 as a
mechanical component for controlling melt flow from a main feed channel 13 and
common manifold feed channel 13d disposed in manifold 15 to a pair of down
drop
bores or nozzles 20d and exit apertures 9a in housings 20e which lead into
cavity 9i.
As shown, the rotary valves 200 comprise a rotatable shaft 202 having a melt
passageway 204, the shaft being rotatably mounted in outer bearing housing
206. As
io shown the outer bearing 206 has a converging/diverging passageway 201 to
match the
inner shaft passageway 204. The rotary shaft 202 is rotatably drivable by its
interconnection to actuator 208 which may comprise an electrically,
pneumatically,
hydraulically or mechanically powered mechanism which is typically
mechanically
interconnected to shaft 202. Automatic control of the actuators is effected in
the same
l5 manner as described above via CPU and PID1 and P1D2 controllers wherein
signals are
sent 210 from sensors 69 to the PID controllers and processed via CPU which,
according
to a predetermined algorithm signals the PID controllers to instruct actuators
208 to
adjust the rotation of passageways 204 so as to vary the rate of melt flow
through
passageways 204 to achieve the predetermined target pressure or pressure
profile at the
20 position of sensors 69. Melt flow through passageways 204 can be precisely
varied
depending on the position of rotation of shaft 202 within bearing 206. As
shown in Fig.
15, passageway 204c in the position shown is fully closed off from manifold
passageway
201 and flow is completely stopped. As can be readily imagined, rotation of
shaft 202,
Fig. 15 in direction 202a will eventually open a leading edge of passageway
204 into
25 open communication with manifold passageway 201 allowing melt to flow and
gradually
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increase to a maximum flow when the passageway 204 reaches the position 204o,
Fig.
15. As described above with reference to other embodiments, the nozzle bores
20d may
exit into a single cavity 9i or may exit into separate cavities (not shown).
Figs. 16-17 show mechanical limit stops that may be employed whereby
prismatic stops 212, 213 attached to the bearing housing 206 serve to engage
radial stops
215 of stop member 214 which is attached to the top of shaft 202 and thus
serve to limit
the rotational travel of shaft 202 in directions 202a and 202b.
Figs. 19-21 show an alternative embodiment where the actuators 208 commonly
drive both a rotary valve 200 and a valve pin 41. As shown the valve pins 41
can be
arranged so as to reciprocate along their axes X between open, 41', and closed
,41,
aperture 9a positions simultaneously with shaft 202 being controllably
rotated. Such
simultaneous drive is accomplished via drive wheel 2.20, Figs. 20-21, whose
gear teeth
228 are meshed with gear teeth 226 of wheel 218 and the screwable engagement
of the
threaded head 234 of pins 41, 41' in the shafts 236 of driven wheels 220. As
can be
readily imagined as shaft 236 is rotated either clockwise or counterclockwise
24, pin 41'
will be displaced either up or down 232 simultaneously with rotation of shaft
202 and its
associated passageway 204. During a typical operation, the rotary valve may
fully stop
the melt flow prior to the valve pin closing at the exit 9a. Similarly, the
valve pin may
open access to the mold cavity 9i prior to the rotary valve permitting melt
through the
passageway 204.
Fig. 22 shows an example of an electrically powered motor which may be used as
an actuator 301, in place of a fluid driven mechanism, for driving a valve pin
or rotary
valve or other nozzle flow control mechanism.. In the embodiment shown in
Figs. 22 a
shaftless motor 300 mounted in housing 302 has a center ball nut 304 in which
a screw
308a is screwably received for controlled reciprocal driving 308 of the screw
308a along
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axis X. Other motors which have a fixed shaft in place of the screw may also
be employed as
described more fully in US Patent No. 6,294,122. As shown in the Fig. 22
embodiment the
nut 304 is rigidly interconnected to magnet 310 and mounting components 31 Oa,
31 Ob
which are in turn fixedly mounted on the inner race of upper rotational
bearing 312 and
lower rotational bearing 314 for rotation of the nut 304 relative to housing
302 which is
fixedly interconnected to the manifold 15 of the injection molding machine.
The axially
driven screw 308a is fixedly interconnected to valve pin 41 which reciprocates
308 along
axis X together with screw 308a as it is driven. As described more fully
below, pin 41 is
io preferably readily detachably interconnected to the moving component of the
particular
actuator being used, in this case screw 3 08a. In the Fig. 22 embodiment, the
head 41 a of
pin 41 is slidably received within a complementary lateral slot 321 provided
in
interconnecting component 320. The housing 302 may be readily detached from
manifold 15 by unscrewing bolts 342 and lifting the housing 302 and sliding
the pin head
41 a out of slot 321 thus making the pin readily accessible for replacement.
As can be readily imagined other motors may be employed which are suitable for
the particular flow control mechanism which is disposed in the flow channel of
the
manifold or nozzle, e.g. valve pin or rotary valve. For example, motors such
as a motor
having an axially fixed shaft having a threaded end which rotates together
with the other
rotating components of the actuator 301 and is screwably received in a
complementary
threaded nut bore in pin interconnecting component 320, or a motor having an
axially
fixed shaft which is otherwise screwably interconnected to the valve pin or
rotary valve
may be employed.
Controlled rotation 318 of screw 308a, Fig 22, is achieved by interconnection
of
the motor 300 to a motor controller 316 which is in turn interconnected to the
CPU, the
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algorithm of which (including PID controllers) controls the on/off input of
electrical
energy to the motor 300, in addition to the direction and speed of rotation
318 and the
timing of all of the foregoing. Motor controller 316 may comprise any
conventional
motor control mechanism(s) which are suitable for the particular motor
selected. Typical
motor controllers include an interface 316a for processing /interpreting
signals received
from the CPU; and, the motor controllers typically comprise a voltage,
current, power or
other regulator receiving the processed/interpreted signals from interface
316a and
regulates the speed of rotation of the motor 300 according to the instruction
signals
received.
Figs. 23, 24 show another embodiment of the invention where a readily
detachable valve pin 41 interconnection is shown in detail. Fig. 23 shows a
nozzle 21 a
having a configuration similar in design to the nozzle configuration of Fig.
13. As
shown the nozzle 21 a is mounted in an aperture in a mold plate 27 having an
exit
aperture aligned with gate 9a and a sensor 69a for measuring a material
property in the
cavity 9g which sends recordation signals to electronic controllers (including
CPU, PID
controllers or the like) for reciprocation of the pin 41 according to a
predetermined
program. In the embodiment shown the pin 41 is straight, however the pin 41
and the
nozzle bore 20 may have other configurations such as showm'described with
reference to
Figs. 2-5 and the sensor 69 located in the nozzle bore 20 or other location in
the path of
the melt flow depending on the type and purpose of control desired for the
particular
application. As described above,, the ready detachability of the pin and
actuator of the
Figs. 23, 24 embodiment may also be adapted to an electric actuator such as
described
with reference to Fig. 22.
Figs. 23-28 illustrate another embodiment of the invention wherein certain
components provide common fluid feed to a plurality fluid driven actuators and
where
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certain components are readily attachable and/or detachable as described in US
Patent No.
5,948,448. As shown in Figs. 23, 24 a fluid driven actuator 322 is fixedly
mounted on a
hotrunner manifold 324 having a melt flow channel 326 leading into nozzle bore
20. The
actuator comprises a unitary housing 328 which sealably encloses a piston 332
having an
0-Ring seal 334 which defines interior sealed fluid chambers, upper chamber
336 and
lower chamber 338. The unitary housing 328 is spacedly mounted on and from the
manifold 324 by spacers 340 and bolts 342 and an intermediate mounting plate
344
attached to the upper surface of the manifold 324. The heads 343 of the bolts
342 are
readily accessible form the top surface 341 of the actuator housing 328 for
ready
detachment of the housing from plate 344 as shown in Figs. 24. Plate 344 is
fixedly
attached to the manifold via bolts 330.
The piston 332 has a stem portion 346, Figs. 23-25, which extends outside the
interior of the sealed housing 328 and chambers 336, 338. At the end of the
stem 346 a
lateral slot 321 is provided for readily slidably receiving in a lateral
direction the head
41 a of the pin. As can be seen the bottom of the slot 321 has an aperture
having a width
less than the diameter of the pin head 41 a such that once the pin head is
slid laterally into
the slot 321, the pin head is held axially within slot 321. In practice the
pin head 41a
and slot 321 are configured so that the pin head 41 a fits snugly within the
slot. As can be
readily imagined, the pin head 41 a can be readily slid out of the slot 321
upon
detachment of the actuator 328, Fig. 24, thus obviating the prior art
necessity of having
to disassemble the actuator itself to obtain access to the pin head 41 a. Once
the actuator
housing is detached, Fig. 24, the pin 41 is thus readily accessible for
removal from and
replacement in the manifold 324/nozzle bore 20.
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In another embodiment of the invention, where hydraulic or pneumatic actuators
are used to drive the pins or rotary valves of two or more nozzles, the drive
fluid may be
supplied by a common manifold or fluid feed duct. Such common fluid feed ducts
are
most preferably independent of the fluid driven actuators, i.e. the ducts do
not comprise a
housing component of the actuators but rather the actuators have a self
contained
housing, independent of the fluid feed manifold, which houses a sealably
enclosed cavity
in which a piston is slidably mounted. For example, as shown in Figs. 23-28,
the fluid
input/output ports 350, 352, 350a, 352a of independent actuators 322, 322a
(Fig 28) are
sealably mated with the fluid input output ports 354, 356, 354a, 356a of a
fluid manifold
358, 358a which commonly delivers actuator drive fluid (such as oil or air) to
the sealed
drive chambers 336, 338, 336a, 338a of two or more actuators 322, 322a. Most
preferably, the ports 354, 356 (or 354a, 356a) of the manifold 358 (or 358a)
are sealably
mated with their complementary actuator ports 350, 352 (350a, 352a) via
compression
mating of the undersurface 360 of the manifold 358 (358a) with the upper
surface 341 of
the actuators 322 (322a) as best shown in Fig. 25. Such compression mating may
be
achieved by initially connecting the manifold via bolt 363 and threaded holes
351 or
similar means to the actuators 322 in their room temperature state (referred
to as cold)
with their mating surfaces in close or mating contact such that upon heating
to operating
temperature the manifold and actuators expand and the undersurfaces 360 and
upper
surfaces 341 compress against each other forming a fluid seal against leakage
around the
aligned ports 350/354 and 352/356. In most preferred embodiments, a
compressible 0-
ring seal 364 is sealed within a complementary receiving groove disposed
around the
mating area between the ports such that when the manifold and actuators are
heated to
operating temperature the O-ring is compressed between the undersurface 360
and upper
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surface 341 thus forming a more reliable and reproducible seal with less
precision in
mounting alignment between the manifold and the actuators being required.
As shown in Figs 23, 25-28, the manifold(s) 322 has two feed ducts 365, 367
for
delivery of pressurized actuator drive fluid to and from a master tank or
other source (not
shown) which ducts extend the length of the manifold 358 and commonly feed
each
actuator 322. In the embodiment shown in Figs. 26, 27 the manifold 358 can be
constructed as a modular apparatus having a first distributor arm 358d
generally
adaptable to be mounted on a hotrunner manifold, to which one or more
additional
distributor amts 358c may be sealably attached 358e to fit/adapt to the
specific
configuration of the particular manifold or injection molding machine to be
outfitted.
As can be readily imagined a plurality of actuators may also utilize a
manifold
plate which forms a structural component of one or more of the actuators and
serves to
deliver drive fluid commonly to the actuators, e.g. the manifold plate forms a
structural
wall portion of the housings of the actuators which serves to form the fluid
sealed cavity
within which the piston or other moving mechanism of the actuator is housed.
Precise control over the piston or other moving component of a fluid driven
actuator such as actuator 322a, Fig. 28, actuator 49, Fig. I . actuator 208,
Fig. 14 (which
more typically comprises an electrically driven actuator), or actuator 322,
Figs 23-27 can
be more effectively carried out with a proportional valve 370 as shown in Fig.
28,
although other valve or drive fluid flow controllers may be employed.
In the Fig. 28 embodiment, a separate proportional valve 370 for each
individual
actuator 322a is mounted on a common drive fluid delivery manifold 358a. The
manifold 358a has a single pressurized fluid delivery duct 372 which feeds
pressurized
drive fluid first into the distributor cavity 370a of the valve 370. The
pressurized fluid
from duct 372 is selectively routed via left 375 or right 374 movement of
plunger or
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spool 380 either through port 370b into piston chamber 338a or through port
370c into
piston chamber 336a. The plunger or spool 380 is controllably movable to any
left to
right 375, 374 position within sealed housing 381 via servo drive 370e which
receives
control signals 382 from the CPU. The servo drive mechanism 370e typically
comprises
an electrically driven mechanism such as a solenoid drive, linear force motor
or
permanent magnet differential motor which is, in turn, controlled by and
interconnected
to CPU via interface 3 84 which interprets and communicates control signals
from the
CPU to the servo drive 370e. Restrictors or projections 370d and 370g of
plunger/spool
380 are slidable over the port apertures 370 b and c to any desired degree
such that the
rate of flow ofpressuriied fluid from chamber 370a through the ports can be
varied to
any desired degree by the degree to which the aperture ports 370b, 370g are
covered over
or restricted by restrictors 370d, 370g. The valve 370 includes left and right
vent ports
which communicate with manifold fluid vent channels 371, 373 respectively for
venting
pressurized fluid arising from the left 375 or right 374 movement of the
plunger/spool
is 380. Thus, depending on the precise positioning of restrictors 370d and
370g over
apertures 370b and 370c, the rate and direction of axial movement of piston
385 and pin
41/head 43, can be selectively varied and controlled which in turn controls
the rate of
melt material from manifold channel 19 through nozzle bore 20 and gate 9. The
nozzle
and pin 41, head 43, and mounting component 87, 89 configurations shown in
Fig. 28
correspond to the configurations shoe in Fig. 5 and the description above with
regard to
the manner in which the melt material is controllable by such head 43,
configurations are
applicable to the Fig. 28 embodiment. A pressurized fluid distributing valve
and a fluid
driven actuator having a configuration other than the proportional valve 370
and actuator
shown in Fig. 28 may be utilized, the essential requirements of such
components being
that the valve include a fluid flow control mechanism which is capable of
varying
RECTIFIED SHEET (RULE 91) ISA/EP
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38
the rate of flow to the drive fluid chambers of the actuator to any desired
rate and
direction of flow into and out of the fluid drive chambers of the actuator.
In the embodiment shown in Figs. 29, 30, a nozzle 21 having a main bore 20
having a main axis X terminates in a gate interfacing bore having an axis Y
which is not
aligned with axis X. As shown the gate 9b of the mold having cavity 9c is an
edge gate
extending radially outward through a mold cavity plate 27 wherein the nozzle
has a bore
having a first portion 20 having an inlet for the plastic melt which is not in
alignment
with the edge gate and a second portion 20f extending radially outward from
the first
portion 20 terminating in the exit aperture of the radial bore 20f being in
alignment with
the edge gate 9b. In the preferred embodiment shown and as described more
fully in US
Patent No. 5, 885, 628, a small gap 9d is left between the radial tip end of
the outer piece
39 of the nozzle and the surface of the mold plate around the cavity 9c such
that it is
possible for melt material to seep from groove 9k through the gap 9d and into
the space
9j circumferentially surrounding the outer piece 39 where the gap 9d is
selected to be
small enough to prevent seepage of plastic melt backwards from space 9j into
the groove
area 9k and gate 9b area during ongoing or newly started up pressurized melt
injection.
The tip end of the nozzle as shown in Figs. 29, 30 comprises an outer 39 piece
and an
inner 37 piece having a gap 6b therebetween. The two pieces 37, 39 are mounted
to
nozzle body 410 which is mounted in thermal isolation from mold 27 together
with
nozzle pieces 37, 39 in a well 408 in the mold 27 via a collar 407 which makes
limited
mounting contact with the mold at small interface area 412 distally away from
the gate 9b
area. As shown surfaces 413, 415 of collar 407 support and align nozzle body
410 and its
associated/interconnected nozzle components 37, 39 such that the exit passage
of nozzle
component 37 along axis Y is aligned with the edge gate 9b of cavity 9c.
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39 -
As shown in Fig. 29 a sensor 69, such as a pressure transducer, records a
property
of the melt material in bore 20 downstream of the, pin head 43 having a
configuration
similar to the embodiment shown in Fig. 3. The signal from sensor 69 is fed to
the CPU
and processed as described above with reference to other embodiments and
instruction
signals based on a predetermined algorithm are sent from the CPU to an
interface 400
which sends interpreted signals to the driver 402, such as drive motor 402
which drives
the drive fluid feed to actuator 322a (as shown having the same design as the
actuator
shown in Fig. 28 which is described in detail in US Patent No. 5,894,025. As
shown in
Fig. 30, a sensor 69d could be positioned so as to sense a property of the
melt flow within
the passage 20, or within the cavity 9c via a sensor 69i. As shown in Fig. 29
and as
described above, the algorithm of the CPU is simultaneously controlling the
operation of
the actuator 420 associated with another nozzle (not shown) via sensor signals
sent by a
sensor associated with the other nozzle.
Fig. 31 shows an embodiment of the invention in which a defined volume of
plastic melt is initially fed into a channel 585 and pot bore 640, prior to
injection to
cavity 9g through nozzle bore 20. As shown, a valve pin 580 is used to close
off the
flow connection from a main bore 620 into a distribution manifold 515, between
the
manifold channel 582 and bores 585/640/20 thus defining a predetermined
defined
volume of melt which can be controllably injected via an injection cylinder
565 which is
controllably drivable via actuator 514 to shoot/inject the defined volume of
melt material
through the bore 20 into cavity 9g. The rate of flow of the melt being
injected via
cylinder 565 may be controlled via controlled operation of any one or more of
a'rotary
valve 512, valve pin 20 or via the drive of the cylinder 565 itself. Cylinder
565 is
controllably drivable back and forth 519 within bore 640 via actuator 514 in a
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conventional manner to thus control the rate of injection of melt from bore
640 through
bore 20.
In accordance with the invention, sensor 69 records a selected condition of
the
melt and sends signals to CPU which in turn may be programmed according to a
predetermined algorithm to control the operation of any one or more of
actuator 545
which controls operation of pin 41, actuator 516 which controls operation of
rotary valve
512 or actuator 514 which controls operation of cylinder 565. As described
above with
regard to other embodiments sensor 69 may alternatively be located in other
locations,
e.g. cavity 9g or bores 640 or 585 depending on the melt properties (typically
pressure)
to be monitored/controlled and the molding operation(s) to be controlled. As
shown in
Fig. 31 and as described above, the algorithm of the CPU is simultaneously
controlling
the operation of the actuator 518 associated with another nozzle (not shown)
via sensor
signals sent by a sensor associated with the other nozzle.
