U.S. patent application number 13/207625 was filed with the patent office on 2011-12-01 for injection molding flow control apparatus and method.
This patent application is currently assigned to Synventive Molding Solutions, Inc.. Invention is credited to Sergio Antunes, Mark Doyle, Christopher W. Lee, Mark Moss, Michael Vasapoli.
Application Number | 20110291328 13/207625 |
Document ID | / |
Family ID | 23583992 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110291328 |
Kind Code |
A1 |
Vasapoli; Michael ; et
al. |
December 1, 2011 |
INJECTION MOLDING FLOW CONTROL APPARATUS AND METHOD
Abstract
Apparatus for controlling the rate of flow of fluid material
through an injection molding flow channel leading to a gate of a
mold cavity, the apparatus comprising: a pin having a longitudinal
length being adapted for back and forth axial movement through the
flow channel; the pin having a protrusion having a maximum diameter
circumferential surface; the channel having an interior surface
complementary to the maximum diameter circumferential surface of
the protrusion; the pin being slidable to a position within the
channel such that the maximum diameter circumferential surface of
the protrusion forms a seal with the complementary interior surface
portion of the channel to stop flow of the fluid material, an
electrically powered actuator interconnected to and controllably
driving the pin through the channel.
Inventors: |
Vasapoli; Michael;
(Gloucester, MA) ; Antunes; Sergio; (Scottsdale,
AZ) ; Moss; Mark; (Boxford, MA) ; Lee;
Christopher W.; (Beverly, MA) ; Doyle; Mark;
(Newburyport, MA) |
Assignee: |
Synventive Molding Solutions,
Inc.
Peabody
MA
|
Family ID: |
23583992 |
Appl. No.: |
13/207625 |
Filed: |
August 11, 2011 |
Related U.S. Patent Documents
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12239922 |
Sep 29, 2008 |
8016581 |
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13207625 |
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12181433 |
Jul 29, 2008 |
7569169 |
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12239922 |
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11757577 |
Jun 4, 2007 |
7419625 |
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12181433 |
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10455881 |
Jun 6, 2003 |
7234929 |
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11757577 |
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11837610 |
Aug 13, 2007 |
7597828 |
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10455881 |
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11351243 |
Feb 9, 2006 |
7270537 |
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11837610 |
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10328457 |
Dec 23, 2002 |
7029268 |
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11351243 |
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10269927 |
Oct 11, 2002 |
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10455881 |
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09400533 |
Sep 21, 1999 |
6464909 |
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10269927 |
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09063762 |
Apr 21, 1998 |
6361300 |
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Dec 9, 2002 |
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Mar 16, 1999 |
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Current U.S.
Class: |
264/328.1 ;
425/166 |
Current CPC
Class: |
B29C 2945/76277
20130101; B29C 2945/76595 20130101; B29C 2945/76006 20130101; B29C
45/30 20130101; B29C 45/766 20130101; B29C 2945/7621 20130101; B29C
2945/76013 20130101; B29C 2945/76943 20130101; B29C 2045/306
20130101; B29C 2945/76785 20130101; B29C 2045/2882 20130101; B29C
2945/76849 20130101; B29C 2045/2772 20130101; B29C 45/2806
20130101; B29C 2945/76735 20130101; B29C 45/2701 20130101; B29C
2045/304 20130101; B29C 2945/76083 20130101; B29C 2945/76591
20130101; B29C 2045/2872 20130101; B29C 2045/2687 20130101; B29C
45/82 20130101; B29C 45/77 20130101; B29C 45/7686 20130101; B29C
45/02 20130101; B29C 45/76 20130101; B29C 2945/76307 20130101; B29C
2945/76581 20130101; B29C 2945/76498 20130101; B29C 2045/2722
20130101; B29C 2045/2886 20130101; B29C 45/768 20130101; B29C
2945/76545 20130101; B29C 2945/76765 20130101; B29C 45/2725
20130101 |
Class at
Publication: |
264/328.1 ;
425/166 |
International
Class: |
B29C 45/77 20060101
B29C045/77 |
Claims
1. Apparatus for controlling the rate of flow of fluid material
through an injection molding flow channel leading to a gate of a
mold cavity, the apparatus comprising: a pin having a longitudinal
length being adapted for back and forth axial movement through the
flow channel; the pin having a protrusion at a selected position
along its length, the protrusion having an upstream end and a
downstream end and a maximum diameter circumferential surface
intermediate the upstream and downstream ends; the channel having
an interior surface area portion which is complementary to the
maximum diameter circumferential surface of the protrusion of the
pin; the pin being slidable to a position within the channel such
that the maximum diameter circumferential surface of the protrusion
forms a seal with the complementary interior surface portion of the
channel to stop flow of the fluid material, an electrically powered
actuator interconnected to and controllably driving the pin through
the channel.
2. The apparatus of claim 1 wherein the electrically driven
actuator is controllably driven to vary the position of the
protrusion to vary the rate of flow of fluid material between the
protrusion and the complementary interior surface portion of the
channel according to a predetermined profile over the course of an
injection cycle that is indicative of the rate of flow of fluid
material.
3. The apparatus of claim 2 wherein the contour of the protrusion
at the upstream or downstream end of the protrusion is
curvilinear.
4. The apparatus of claim 1 wherein the pin is drivable through at
least a first position wherein fluid flow is stopped when the
maximum diameter circumferential surface of the protrusion mates
with the complementary interior channel surface and a second
upstream position where fluid flow is enabled between the
downstream end of the protrusion and the complementary interior
channel surface of the channel and a third downstream position
where fluid flow is enabled between the upstream end of the
protrusion and the complementary interior channel surface of the
channel.
5. The apparatus of claim 4 wherein the contour of the protrusion
at the upstream or downstream end of the protrusion is
curvilinear.
6. The apparatus of claim 1 wherein the pin has a terminal end
downstream of the protrusion and is adapted to be drivable through
a downstream position where the terminal end of the pin downstream
of the protrusion is controllably engageable with a complementary
exit aperture of the channel immediately adjacent to an entrance
port to the mold to prevent flow through the exit aperture.
7. The apparatus of claim 1 wherein the maximum diameter
circumferential surface of the bulbous protrusion is cylindrical in
shape.
8. The apparatus of claim 1 wherein the complementary interior
surface portion of the channel is cylindrical in shape.
9. The apparatus of claim 1 wherein the pin has a stem slidably
mounted in a bore of a mounting member, the bore having a diameter
equal to or greater than the maximum diameter circumferential
surface of the protrusion of the pin.
10. The apparatus of claim 1 wherein the complementary interior
surface portion of the channel is disposed upstream of a gate area
of the mold, the pin being adapted to be selectively positionable
such that the protrusion is selectively positionable relative to
the complementary interior surface portion of the channel to
controllably vary the rate of fluid flow.
11. The apparatus of claim 1 further comprising: a sensor for
sensing a selected condition of the fluid or position of the pin or
a force that drives movement of the pin; a computer interconnected
to the sensor for receiving a signal representative of the sensed
condition, position or force from the sensor, the computer
including an algorithm utilizing a value corresponding to the
signal received from the sensor as a variable for controlling
operation of an actuator that is drivably interconnected to the
pin.
12. The apparatus of claim 1 wherein the pin is adapted to prevent
flow of fluid by moving the pin from a downstream position to an
upstream position and to increase flow by moving the pin from an
upstream position to a downstream position.
13. A method of controlling the rate of flow of fluid through a
flow channel communicating with a gate of a mold in an injection
molding apparatus, the apparatus including a valve pin having a
selected longitudinal length that is slidably mounted in a housing
that is adapted for back and forth axial movement of the pin
through the flow channel, the method comprising: forming the pin
with a protrusion at a selected position along its length wherein
the protrusion has an upstream end and a downstream end, mounting
the pin such that the protrusion is controllably drivable back and
forth within the channel, forming the protrusion with a maximum
diameter outer circumferential surface between its upstream and
downstream ends; forming the channel with an interior surface area
portion which is complementary to the maximum diameter
circumferential surface such that the maximum diameter outer
circumferential surface of the protrusion is matable with the
interior surface area portion of the channel to stop flow of the
fluid through the channel during driving of the pin; controlling
driven movement of the pin through the channel with an electrically
powered actuator interconnected to the pin.
14. The method of claim 13 wherein the electrically powered
actuator is controllably driven to selectively position the maximum
diameter circumferential surface of the protrusion at controllably
selectable positions relative to the interior surface area portion
of the channel such that the rate of flow of the fluid through the
channel is controllably variable.
15. The method of claim 13 wherein the complementary interior
surface area portion of the channel is disposed at a position
upstream of and away from the gate of the mold.
16. The method of claim 13 further comprising controlling movement
of the pin to position the downstream end of the protrusion at
controllably selectable distances relative to the interior surface
area portion of the channel such that the rate of flow of fluid
between the downstream end and the interior surface area portion is
controllably variable.
17. The method of claim 13 further comprising controlling movement
of the pin to position the upstream end of the protrusion at
controllably selectable distances relative to the interior surface
area portion of the channel such that the rate of flow of fluid
between the downstream end and the interior surface area portion is
controllably variable.
18. The method of claim 13 further comprising: sensing a selected
condition of the fluid, a position of the pin or a force driving
the pin; controlling movement of the pin within the channel
according to an algorithm that determines a position for movement
of the pin based on the use as a variable of a value indicative of
the selected condition, position or force that is sensed in the
step of sensing.
19. The method of claim 13 further comprising: forming the aperture
in the housing in which the pin is slidably mounted and the pin to
have a diameter equal to or greater than the maximum diameter
circumferential surface of the protrusion of the pin.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35 USC
Section 119 to U.S. provisional patent application Ser. No.
60/431,923 filed Dec. 9, 2002, the disclosure of which is
incorporated herein by reference in its entirety as if fully set
forth herein.
[0002] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/269,927 filed Oct. 11, 2002 which is a
continuation of U.S. application Ser. No. 09/400,533 issued as U.S.
Pat. No. 6,464,909 on Oct. 15, 2002.
[0003] The disclosures of all of the following are incorporated by
reference in their entirety as if fully set forth herein: U.S. Pat.
No. 5,894,025, U.S. Pat. No. 6,062,840, U.S. Pat. No. 6,294,122,
U.S. Pat. No. 6,309,208, U.S. Pat. No. 6,287,107, U.S. Pat. No.
6,343,921, U.S. Pat. No. 6,343,922, U.S. Pat. No. 6,254,377, U.S.
Pat. No. 6,261,075, U.S. Pat. No. 6,361,300 (7006), U.S. Pat. No.
6,464,909 (7031), U.S. patent application Ser. No. 10/214,118,
filed Aug. 8, 2002 (7006), U.S. Pat. No. 7,029,268 (7077US1), U.S.
patent application Ser. No. 09/699,856 filed Oct. 30, 2000 (7056),
U.S. patent application Ser. No. 10/269,927 filed Oct. 11, 2002
(7031), U.S. application Ser. No. 09/503,832 filed Feb. 15, 2000
(7053), U.S. application Ser. No. 09/656,846 filed Sep. 7, 2000
(7060), U.S. application Ser. No. 10/006,504 filed Dec. 3, 2001,
(7068) and U.S. application Ser. No. 10/101,278 filed Mar. 19, 2002
(7070).
BACKGROUND OF THE INVENTION
[0004] Injection molding systems have been developed having flow
control mechanisms that move at high speed over relatively short
periods of time to control the rate of flow of fluid material that
is being injected to a mold cavity. The range of distance of
movement or travel of the flow control mechanisms is also
relatively small. Computer/algorithm electronic controls have been
developed to effect such movements on the basis of a variable input
that corresponds to a sensed condition of the fluid material being
injected or another sensed property, state or condition of a
component of the apparatus or the energy, pressure or power used to
operate an operating mechanism associated with the apparatus that
is used to control the flow velocity of the fluid material.
[0005] The accuracy and precision of such algorithmically
controlled movement depends on the accuracy/precision of the sensed
condition as a measure of flow velocity at any given point in time
or at any given location within the fluid flow stream where the
fluid or machine property is being sensed by a sensor.
SUMMARY OF THE INVENTION
[0006] In accordance with the invention there is provided an
injection molding apparatus comprising: a manifold having a channel
for delivering a flow of a fluid material to a gate of a mold
cavity during an injection cycle; a fluid flow controller adapted
to move within the channel along a path of travel; a position
sensor for detecting one or more positions of the fluid flow
controller along the path of travel; a master controller
interconnected to the fluid flow controller for controlling
movement of the fluid flow controller along the path of travel, the
master controller including an algorithm having a set of
instructions that limit the extent of travel of the fluid flow
controller along the path of travel during the injection cycle to
one or more preselected positions, the one or more preselected
positions being detected by the position sensor, the position
sensor sending a signal indicative of detection of the one or more
preselected positions of travel to the master controller during the
injection cycle, the master controller limiting travel of the fluid
flow controller beyond the one or more preselected positions upon
receipt of the signal.
[0007] The one or more preselected positions typically comprise one
or more positions at which the fluid flow controller allows flow of
the fluid material through the channel at a maximum rate of
flow.
[0008] The algorithm can include a set of instructions that control
movement of the fluid flow controller beyond the one or more
preselected positions upon occurrence of a predetermined event
during the injection cycle. The predetermined event typically
comprises one or more of (a) an expiration of a predetermined
amount of time from a selected point in time during an injection
cycle, (b) detection of a selected degree of a condition of the
fluid material or (c) detection of a selected degree of a selected
property, position or operating condition of an operating component
of the hotrunner/manifold apparatus or the injection molding
machine.
[0009] The fluid flow controller is preferably movable along the
path of travel between a range of variable flow rate positions, a
range of maximum flow positions and one or more closed flow
positions, wherein the one or more preselected positions to which
travel of the flow controller is limited during the injection cycle
comprise one or more of the maximum flow positions.
[0010] The apparatus preferably further comprises a material
condition sensor that senses a selected condition of the fluid
material, the algorithm utilizing a value indicative of the sensed
condition as a variable to control movement of the fluid flow
controller to one or more variable flow rate positions along the
path of travel. The material condition sensor typically comprises a
pressure sensor.
[0011] The fluid flow controller typically comprises a valve pin
having a first end interconnected to an actuator and a control
surface distal of the first end that is movable to a plurality of
varying flow rate positions, the actuator being interconnected to
the algorithm, the algorithm including a set of instructions for
controlling movement of the control surface to the one or more
varying flow rate positions during the injection cycle.
[0012] The valve pin can have a second end that closes the gate in
a forward closed position, the control surface being intermediate
the first and second ends and controllably movable to the plurality
of varying flow rate positions. The valve pin is preferably movable
between the plurality of varying flow rate positions, a range of
maximum flow positions and the forward closed position, wherein the
one or more preselected positions to which travel of the flow
controller is limited during the injection cycle comprise one or
more of the maximum flow positions.
[0013] Upstream movement of the valve pin to successive ones of the
plurality of varying flow rate positions typically decreases the
rate of flow of fluid material.
[0014] In another aspect of the invention there is provided an
injection molding apparatus comprising a manifold having a channel
for delivering a flow of a fluid material to a gate of a mold
cavity during an injection cycle; a valve pin adapted to
reciprocate through the channel along a path of travel; a condition
sensor for detecting a selected condition of the fluid material; a
position sensor for detecting one or more positions of the valve
pin along the path of travel; a controller interconnected to the
valve pin for controlling movement of the valve pin along the path
of travel, the controller including an algorithm having a set of
instructions that control movement of the valve pin to a plurality
of varying flow rate positions along the path of travel based on
values determined by the selected condition of the fluid material
sensed by the condition sensor during the injection cycle; the
algorithm including a set of instructions that limit the extent of
upstream or downstream travel of the pin along the path of travel
during the injection cycle to one or more preselected positions,
the one or more preselected positions being detected by the
position sensor, the position sensor sending a signal indicative of
detection of the one or more preselected positions of travel to the
controller during the injection cycle.
[0015] In another aspect of the invention there is provided an
injection molding apparatus comprising a manifold having a channel
for delivering a flow of a selected fluid material to a gate of a
mold; a valve pin adapted to reciprocate through the channel, the
valve pin having a first end coupled to an actuator, a second end
that closes the gate in a forward closed position, and a control
surface intermediate said first and second ends for adjusting the
rate of material flow during an injection cycle, wherein the
actuator is interconnected to a controller having a program for
controlling reciprocation of the valve pin according to a
predetermined algorithm; a condition sensor for detecting a
selected condition of the fluid material, the algorithm utilizing a
value determined by the selected condition detected by the
condition sensor to control reciprocation of the valve pin; a
position sensor that senses position of the valve pin, the
algorithm utilizing a value determined by one or more sensed
positions of the valve pin to limit movement of the valve pin
during the injection cycle beyond the one or more sensed positions
during the injection cycle.
[0016] The invention also provides a valve assembly for controlling
fluid flow rate in an injection molding apparatus, wherein the
assembly comprises:
[0017] an actuator comprising a housing and a driven piston
slidably disposed within the housing for reciprocal movement within
the housing to one or more fluid flow rate control positions, the
actuator being interconnected to a fluid flow controller and a
master controller having an algorithm that includes a set of
instructions for controlling movement of the piston;
[0018] a position sensor adapted to sense movement of the piston or
the fluid flow controller, the position sensor being interconnected
to the master controller for sending signals indicative of the
position of the piston to the master controller, the algorithm
utilizing values corresponding to the signals sent by the position
sensor.
[0019] The invention further provides a method for controlling
injection of a fluid through a gate of a mold cavity in an
injection molding apparatus, the injection molding apparatus
comprising a manifold having a channel for delivering a flow of the
fluid material to the gate of the mold cavity during an injection
cycle and a fluid flow controller adapted to be moved by an
actuator to a plurality of positions along a path of travel within
the channel, the method comprising:
[0020] predetermining one or more positions along the path of
travel during an injection cycle that generate a rate of flow of
the fluid material by the fluid flow controller that fills the mold
cavity with the fluid material according to a predetermined profile
of one or more positions;
[0021] injecting the fluid through the channel;
[0022] sensing the one or more positions of the fluid flow
controller along the path of travel;
[0023] sending signals corresponding to the sensed one or more
positions to a controller for controlling movement of the fluid
flow controller to the predetermined one or more positions along
the path of travel according to an algorithm;
[0024] inputting values corresponding to the sent signals to the
algorithm, the algorithm having a set of instructions that compare
the input values to a stored set of values corresponding to the
predetermined one or more positions and a set of instructions that
instruct the actuator to move the fluid flow controller to the
predetermined one or more positions during the injection cycle.
[0025] There is also provided a method for controlling injection of
a fluid through a gate of a mold cavity in an injection molding
apparatus, the injection molding apparatus comprising a manifold
having a channel for delivering a flow of the fluid material to the
gate of the mold cavity during an injection cycle and a fluid flow
controller adapted to be moved by an actuator to a plurality of
positions having a pressure at each position along a path of travel
within the channel, the method comprising:
[0026] predetermining one or more pressures of the fluid material
corresponding to a respective one or more positions of the fluid
flow controller along the path of travel that generate a rate of
flow of the fluid material by the fluid flow controller that fills
the mold cavity with the fluid material at a predetermined rate of
fill during the injection cycle;
[0027] injecting the fluid through the channel under pressure
during an injection cycle;
[0028] sensing the pressure of the injected fluid during the
injection cycle;
[0029] sending signals corresponding to the sensed pressure to a
controller for controlling movement of the fluid flow controller
according to an algorithm;
[0030] predetermining a limit position for the fluid flow
controller;
[0031] sensing the position of the fluid flow controller during the
injection cycle;
[0032] sending signals corresponding to the sensed position to the
controller;
[0033] inputting values corresponding to the sent pressure and
position signals to the algorithm, the algorithm having a set of
instructions that compare the input pressure values to a stored set
of values corresponding to the predetermined one or more pressures
and a set of instructions that compare the input position values to
a value corresponding to the predetermined limit position;
[0034] the algorithm including a set of instructions that instruct
the actuator to move the fluid flow controller to the predetermined
one or more positions corresponding to the predetermined one or
more pressures during the injection cycle;
[0035] the algorithm further including a set of instructions that
instruct the actuator to limit movement of the fluid flow
controller to the limit position during selected periods of time
during the injection cycle.
[0036] Further in accordance with the invention therefore, in
injection molding machines and processes, there is provided an
axially slidable pin which is driven in a predetermined path of
axial travel by an actuator which is driven by electrical power,
the actuator being drivably interconnected to the pin. The actuator
may comprise a mechanism which is drivably interconnected to the
rotor of an electrically powered motor (either coaxially along an
axis of the rotor or via some other non-coaxial interconnection
such as a bevel gear, worm gear, rack/pinion/gear, multiple gear or
other interconnection) the driven actuator, in turn, driving
movement of the pin. A frameless motor or a motor having a shaft
may be utilized. The apparatus preferably includes a mechanism for
absorbing forces which may be transmitted from the pin to the rotor
of the motor along its axis. The invention may include a controller
which receives signals generated by one or more sensors which sense
selected conditions of the molten plastic, the controller utilizing
the signals according to a predetermined algorithm and controlling
the drive of the electrically driven actuator according to the
algorithm.
[0037] Apparatuses and methods according to the invention may or
may not include a motor drive controller and the controller may
have an algorithm which does or does not utilize signals/data which
are representative of sensed conditions of the melt or the machine
components.
[0038] In the most preferred embodiments described herein, axial
forces to which the pin is subjected are transmitted to the
actuating mechanism without loading the rotor of the drive motor
along its axis. In embodiments where the motor rotor is coaxially
aligned with the axis of the reciprocating pin, a force absorbing
mechanism is preferably used to absorb the load which would
otherwise be transmitted to the motor along its axis.
[0039] More particularly, there is provided in an injection molding
machine, an apparatus for controlling movement of a pin
comprising:
[0040] a plastic melt flow channel having an output end for
delivering molten plastic injected into the channel under pressure
to a mold cavity, wherein the pin comprises an elongated rod having
an axis and an end, the pin being slidably mounted within the
channel for movement along its axis within the channel,
[0041] an electrically driven motor drivably interconnected to an
actuating mechanism, wherein the actuating mechanism is drivably
interconnected to the end of the pin, the motor being controllably
drivable to drive the pin through movement along its axis within
the channel.
[0042] The motor may include a rotatably driven rotor which
translates motion to the pin to drive the pin along its axis
without rotation. The pin is typically subjected to forces along
its axis wherein the actuating mechanism is interconnected to the
end of the pin such that the axial forces to which the pin is
subjected are transmitted between the pin and the actuating
mechanism without absorption of the axial forces. The apparatus may
include a force absorbing member which absorbs forces transmitted
to the rotor of the motor along its axis. The actuating mechanism
may comprise a screw and a complementary nut screwably engaged with
each other, at least one of the screw and the nut being drivably
interconnected to the motor to travel along a predetermined path of
travel, the pin being simultaneously driven along its axis through
a path of travel according to the predetermined path of travel of
the screw or the nut.
[0043] The motor may be connected to a controller having a program
for driving the movement of the actuating mechanism according to
one or more sensed conditions of the molten plastic or the
injection molding machine. The controller may include a PID
(proportional, integral, derivative) controller. Protocols other
than PID may be utilized. The program for driving the movement of
the actuating mechanism typically includes an algorithm utilizing a
value representative of one or more of the pressure, temperature,
viscosity and flow rate of the molten plastic, the position of a
component of the machine and the time or time lapse of operation of
the machine or a component of the machine. The apparatus may
include a sensor which senses a selected condition of the molten
plastic or the injection molding machine and which generates
signals representative of the sensed property, the controller
having a program which controls the motor according to the
generated signals. The apparatus may also include a recorder or
sensor or monitor which measures, records or monitors the position
of a component of the machine or the time or time lapse of the
operation of the machine or a component of the machine.
[0044] 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.
[0045] There is further provided, in an injection molding machine,
a plastic melt flow control valve apparatus comprising:
[0046] a plastic melt flow channel having an output end for
delivering molten plastic injected into the channel under pressure
to a mold cavity;
[0047] an elongated valve pin having an axis and an end, the pin
being slidably mounted within the channel for movement along its
axis within the channel to control flow of the molten plastic;
[0048] an electrically driven motor drivably interconnected to an
actuating mechanism, wherein the actuating mechanism is
interconnected to the end of the pin, the motor being controllably
drivable to drive the pin through movement along its axis within
the channel.
[0049] There is further provided in an injection molding machine
having a plastic melt flow channel with a pin slidably mounted
within the channel, wherein the channel has an output end for
delivering molten plastic injected into the channel under pressure
to a mold cavity, and wherein the pin comprises an elongated rod
having an axis and an end, the pin being slidably mounted for
movement along its axis within the channel, a method for
controllably driving movement of the pin along its axis
comprising:
[0050] drivably interconnecting a rotatable rotor of an
electrically driven motor to an actuating mechanism which is
drivably movable along a predetermined path of travel;
[0051] interconnecting the actuating mechanism to the end of the
pin such that movement of the actuating mechanism along its
predetermined path of travel simultaneously moves the pin along its
axis according to a predetermined path of travel;
[0052] controllably driving the motor to controllably drive the
actuating mechanism and to controllably drive the pin through its
predetermined path of travel within the channel.
[0053] The rotor of the motor most preferably translates rotational
force to the pin to move the pin along its predetermined path of
travel without rotation of the pin. The method may comprise
interconnecting the actuating mechanism to the end of the pin such
that the axial forces to which the pin is subjected are transmitted
between the pin and the actuating mechanism with or without
absorption of the forces.
[0054] The method may further comprise sensing one or more
conditions of the molten plastic selected from the group consisting
of pressure, temperature, viscosity, force and flow rate of the
molten plastic or recording or measuring one or more of the
position of a component of the machine or the time or time lapse of
the operation of the machine or a component of the machine and
controlling the drive of the motor according to a predetermined
algorithm utilizing a value for the sensed conditions and/or the
recorded/measured positions or times.
[0055] There is also provided in an injection molding system, a
method of opening and closing a gate leading to a mold cavity
comprising controllably driving, with an electrically powered
motor, a pin which is slidably mounted within a channel leading to
the gate along a predetermined path of axial travel in which the
gate is closed by the pin in at least one position and opened by
the pin in at another position along the predetermined path of
travel.
[0056] There is also provided in an injection molding system, a
method of dynamically altering the flow of molten plastic in a melt
flow channel comprising controllably driving, with an electrically
powered motor, a pin which is slidably mounted within the melt flow
channel along a predetermined path of axial travel in which the
flow of the melt through the channel varies according to the
position of the pin along the predetermined path of travel.
[0057] In alternative embodiments, the pin may be interconnected to
the rotor of the electrically powered motor such that the pin is
rotatable and the mechanism for controlling flow of plastic within
the melt flow channel may comprise may comprise plate, cam or other
mechanisms which are drivable to open and close the gate or other
flow passage leading to the mold cavity or to otherwise vary the
rate of flow through the melt flow channel leading to the gate or
other flow passage to the mold cavity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] The above and further advantages of the invention may be
better understood by referring to the following description in
conjunction with the accompanying drawings in which:
[0059] FIG. 1 is a schematic cross-sectional view of one embodiment
of an injection molding system according to the present
invention;
[0060] FIG. 2 is an isometric exploded view of an actuator usable
in the FIG. 1 embodiment showing a linear position sensor mountable
to an outside surface of the actuator housing for use in sensing
the position of the actuator cylinder and its associated valve pin
along its path of travel within the bore/channel of a nozzle
leading to the gate of the mold cavity of the FIG. 1
embodiment;
[0061] FIG. 3 is a partially schematic, side cross-sectional view
of the position sensor mounting arrangement shown in FIG. 2;
[0062] FIGS. 4-6 are side cross-sectional views of an
actuator/pin/nozzle assembly as shown in FIG. 1 showing a linear
position sensor mounted thereon as shown in FIGS. 2, 3, the valve
pin being shown in three operating positions during the course of
an injection cycle, the start closed position shown in FIG. 4, an
intermediate flow enabled position shown in FIG. 5 and a maximum
flow position shown in FIG. 6;
[0063] FIG. 4a is a side cross-sectional view of another embodiment
of the invention showing an actuator/pin/nozzle assembly as shown
in FIG. 1 having a switch that detects the position of the piston
of the actuator through a window by electromagnetic or magnetic
means;
[0064] FIG. 4b is a side cross-sectional view of another embodiment
of the invention showing an actuator/pin/nozzle assembly as shown
in FIG. 1 having a switch that detects the position of the piston
of the actuator by mechanical contact means;
[0065] FIG. 7 is a partially schematic, side cross-section view of
an actuator/pin assembly as shown in FIG. 1 with an alternative
type of inductive position sensor mounted at a rear end of the
actuator for sensing/recording the position of travel of the
cylinder and its associated valve pin;
[0066] FIG. 8 is a flow chart showing an algorithm that can be used
in the master controller of the FIG. 1 system for controlling
movement of the actuator and valve pin during an injection cycle,
the algorithm using as control variables signals that are
indicative of both the position of the cylinder/pin and a selected
property (such as pressure) of the fluid being routed through a
flow channel of the manifold;
[0067] FIGS. 9a-d shows a series of examples of graphs representing
actual pressure versus target pressures measured in four injection
nozzles having position and pressure sensors coupled to a manifold
as shown in FIG. 1;
[0068] FIGS. 10, 11 are screen icons displayed on interface 114 of
FIGS. 5-7 which are used to display, create, edit, and store target
profiles.
[0069] FIG. 12 shows a fragmentary cross-sectional view of a system
similar to FIG. 1, showing an alternative embodiment in which a
forward valve pin shut-off is used;
[0070] FIG. 13 shows an enlarged fragmentary view of the embodiment
of FIG. 6, showing the valve pin in the open and closed positions,
respectively;
[0071] FIG. 14 is a cross-sectional view of an alternative
embodiment of the present invention similar to FIG. 6, in which a
threaded nozzle is used with a plug for easy removal of the valve
pin;
[0072] FIG. 15 is an enlarged fragmentary view of the embodiment of
FIG. 8, in which the valve pin is shown in the open and closed
positions;
[0073] FIG. 16 is an enlarged view of an alternative embodiment of
the valve pin, shown in the closed position;
[0074] FIG. 17 is a fragmentary cross sectional view of an
alternative embodiment of an injection molding system having flow
control that includes a valve pin that extends to the gate;
[0075] FIG. 18 is an enlarged fragmentary cross-sectional detail of
the flow control area;
[0076] FIG. 19 is a side cross-sectional view of valve having a
curvilinear bulbous protrusion and an extended pin, the bulbous
protrusion being in a flow shut-off position;
[0077] FIG. 19A is a close-up view of the bulbous protrusion of
FIG. 32;
[0078] FIG. 20 is a view similar to FIG. 32 showing the bulbous
protrusion in a flow controlling position;
[0079] FIG. 20A is a close-up view of the bulbous protrusion
position of FIG. 33;
[0080] FIG. 21 is a view similar to FIG. 19 showing the bulbous
protrusion in a downstream position and the distal tip end of the
extended pin in a gate flow shut-off position;
[0081] FIG. 21A is a close-up view of the bulbous protrusion
position of FIG. 21;
[0082] FIG. 22 is a side cross-sectional view of valve having a
curvilinear bulbous protrusion, the bulbous protrusion being in a
flow shut-off position and not having a gate shut off distal pin
extension section;
[0083] FIG. 23 is a view similar to FIG. 22 showing the bulbous
protrusion in a flow controlling position;
[0084] FIG. 24 is a side cross-sectional view of valve having a
curvilinear bulbous protrusion, where the pin is mounted in an
aperture in the hot runner which has a diameter equal to the
diameter of the bulbous protrusion such that the pin may be
withdrawn from the actuator and the hotrunner without removing the
actuator from the housing or the mounting bushing from the
hotrunner, and where the bulbous protrusion is in a flow shut-off
position;
[0085] FIG. 24A is a close-up view of the bulbous protrusion in the
flow shut off position of FIG. 24;
[0086] FIG. 25 is a view similar to FIG. 24 showing the bulbous
protrusion in a downstream flow controlling position;
[0087] FIG. 25A is a close-up view of the bulbous protrusion in the
flow controlling position of FIG. 25;
[0088] FIG. 26 is a schematic side cross-sectional view of an
embodiment of a pin having a bulbous protrusion with a maximum
diameter circumferential section which has straight surfaces, e.g.
cylindrical, which complementarily mate with a complementary
straight cylindrical surface on the interior of the flow channel at
a throat section;
[0089] FIG. 27 is a schematic side cross-sectional view of an
embodiment showing a bulbous protrusion similar to FIG. 26 but
where the controlling flow position is upstream of the throat
section of the channel and the flow shut-off position is achieved
or reached by forward or upstream movement of the pin from the
position shown in FIG. 27;
[0090] FIG. 28 is a cross-sectional partially schematic view of
another alternative embodiment of an injection molding system
having flow control in which a load cell behind the valve pin is
used to control the flow rate in each injection nozzle;
[0091] FIG. 29 is a enlarged fragmentary cross-sectional view of
the valve pin and actuator of FIG. 14;
[0092] FIG. 30 is an enlarged view of the load cell and valve pin
of FIG. 14;
[0093] FIGS. 31A and 31B show an enlarged view of the tip of the
valve pin closing the gate and controlling the flow rate,
respectively;
[0094] FIGS. 32A and 32B shown an alternative structure of an
injection molding nozzle for use in the system shown in FIG.
14;
[0095] FIG. 33 is a cross-sectional partially schematic view of an
alternative embodiment of an injection molding system in which a
pressure transducer is used to sense the hydraulic pressure
supplied to the actuator;
[0096] FIG. 34 shows a fragmentary cross-sectional view of an
alternative embodiment of an injection molding system having flow
control similar to FIG. 14 in which the pressure transducer is
mounted in the mold cavity; and
[0097] FIG. 35 is a fragmentary cross-sectional view of an
alternative embodiment of an injection molding system having flow
control in which flow control is effected by measuring the
differential pressure of the actuator chambers;
[0098] FIG. 2a is a side view of an apparatus according to the
invention having an electrically powered actuator;
[0099] FIG. 2b is a cross section along lines B-B of FIG. 2a
showing the shaft of an electric motor interconnected to an
actuator screw with an axial force absorbing bearing mounted
between the housing for the shaft and the housing for the nut and
screw;
[0100] FIG. 3a is an isometric view of an assembled apparatus
according to FIG. 2b;
[0101] FIG. 4aa is an exploded isometric view of the FIG. 3a
apparatus;
[0102] FIG. 5b is a close-up exploded isometric view of the pin,
load cell, coupling and screw/nut components of the FIG. 4a
apparatus;
[0103] FIG. 5a is a schematic side cross sectional view showing
another embodiment of the invention showing a screw screwably
engaged with the rotor of a frameless motor, the screw being
coaxially interconnected directly to a slidably movable pin with an
axial force absorbing bearing mounted between the rotor and the
housing for the rotor;
[0104] FIG. 6a is a side schematic view of another embodiment of
the invention;
[0105] FIG. 6b is a side cross-sectional view along lines A-A of
FIG. 6a showing a bevel gear interconnection between the rotor or a
shaft of an electric motor and an actuator screw;
[0106] FIG. 7a is an isometric view of an assembled FIG. 6b
apparatus;
[0107] FIG. 8a is an exploded isometric view of the FIG. 7a
apparatus.
DETAILED DESCRIPTION
[0108] FIG. 1 shows one embodiment of an injection molding system 1
according to the present invention having a pair of valve gated
nozzles 215 delivering fluid material to gates 211, which in turn
communicate with and deliver fluid material to mold cavity 170.
Fluid material is injected initially under pressure from injection
molding machine barrel 13 into a main injection channel 17 formed
in heated manifold 231 and travels from channel 17 to the bores or
channels 208, 213 of nozzles 215. As shown in FIGS. 1, 4-6 an
embodiment using an extended pin 200 is disposed within channels
208, 213 for slidable reciprocating movement along the axes of
channels 208, 213. Channel 17 mates/communicates with bores 208,
213 at an elbow at which a throat or restricted channel section is
disposed where a gap 207 can be formed for controlling material
flow rate upstream or away from the gate as described below.
[0109] In the FIG. 1 embodiment, a master controller 10 typically
comprising a data processor and memory components for processing
and storing digital data controls the movement of actuators 226
which in turn control the reciprocal movement of pins 200. In the
FIG. 1 embodiment, the master controller 10 receives signals from
both position sensors and material condition sensors. A generic
position sensor is designated as item 100 in FIG. 1. Position
sensor 1000 can comprise a variety of types of position sensing
mechanisms as described below. Although shown mounted on the side
of the housing 225 of actuators 226 in FIG. 1, depending on the
precise type of position sensor and the precise type of actuator or
other mechanical component of the apparatus whose position is to be
measured, position sensor 1000 is mounted in a location that is
most appropriate to sensing the position of the mechanical
component to be monitored.
[0110] As shown in FIG. 1 the master controller 10 sends control
signals to servo-valves 212 which control the input and outflow of
hydraulic or pneumatic fluid to the sealed chambers of actuators
226. The actuators 226 may comprise electrically driven actuators
as described for example in U.S. Pat. No. 6,294,122 the disclosure
of which is incorporated by reference in its entirety as if fully
set forth herein. Servo-control mechanisms can be interconnected
between the master controller 10 and an electric actuator, the
servomechanism receiving the digital signal output of controller 10
for precisely controlling the drive and movement of the shaft of
the electric actuator in the same functional manner as the fluid
driven actuators 26 are described herein. Shooting pot rams or
cylinders as described in U.S. Pat. Nos. 6,464,909 and 6,287,107
can also be used in place of valves and valve pins for controlling
fluid flow according to the invention. In each case where a
particular actuator and its associated servomechanism is used,
whether a valve pin, rotary valve or shooting pot ram/cylinder
controlled by a hydraulically, pneumatically or electrically driven
mechanism, a position sensing mechanism can be used to sense the
travel or position of the pin, rotary valve or ram/cylinder and
send a position indicative signal to the master controller 10 that
includes an algorithm having instructions that use a value
corresponding to the position indicative signal to control movement
of the valve pin, rotary valve or ram/cylinder in a manner as
disclosed and claimed herein.
[0111] Although only two nozzles and gates are shown in FIG. 1, the
invention contemplates embodiments that simultaneously control the
material flow through a plurality of more than two nozzles to a
plurality of gates. In the embodiment shown, the injection molding
system 1 is a single cavity 170 system. The present invention can
be adapted to any of a variety of systems where several nozzle
bores or downstream channels 183, 185 feed two or more cavities of
the same size/configuration or separate cavities of different
size/configuration or where several bores or channels feed a single
non-uniform cavity at different locations/points of entry where the
volumes to be filled at entry are different as described in, for
example, U.S. patent application Ser. No. 10/328,457 filed Dec. 23,
2002, the disclosure of which is incorporated herein by reference
in its entirety as if fully set forth.
[0112] A system according to the invention injects plastic material
which is heated/melted to a fluid form and injected through the
heated manifold 231 which maintains the plastic material in fluid
form. The invention is also applicable to other types of injection
systems in which it is useful to control the rate at which another
fluid material, e.g., metallic or composite materials is delivered
to a cavity of a mold.
[0113] The rate at which fluid material is delivered through the
channels 13, 17, 208, 213 of the FIG. 1 embodiment is controllably
varied by the enlarged bulbous protrusion formed along the length
of the valve pin 200. As shown in FIGS. 1, 4-6 the valve pin 200 is
interconnected at a proximal end to the sliding piston 223 mounted
in cylinder housings 225 of actuators 226 which in turn are
interconnected to servo-controllers 212 which are in turn
interconnected to master controller 10. As shown in the FIGS. 4-6
embodiment, the master computer or controller 10 receives signal
inputs indicative of a position of the valve pins 200 and their
associated pistons 223 from position sensors 100. The position
sensors 100 are mountable on the actuators 226 of FIG. 1 as shown
in FIGS. 2, 3 within a slot 103 that can be provided on the side or
outer surface of cylinder housing 225 that is lateral to the axis
of movement of the piston 223. The position sensors 105 sense the
position of travel or stroke 112 of the pins 200 via a sliding rod
102 interconnected to plate 104 which is attached to a distal end
of piston 223 as shown in FIGS. 2, 4-6. The sliding rod 102 is
spring loaded to maintain contact with the plate at one end and is
interconnected to a potentiometer provided within sensor 105 at
another end. The potentiometer 105 is interconnected via wiring 105
to controller 10 and sends a voltage signal that varies with the
position of the sliding rod 102 which follows and is indicative of
the position of travel or stroke 112 of the pin 200 and the piston
223 to which the pin 200 is connected. The controller 10 receives
the variable voltage signal and converts the signal to a value
indicative of piston 223 and pin 200 position that is processable
by the algorithm. The controller 10 includes an algorithm which
uses as a variable, a value indicative of the position signal
received from sensor 105 to control the movement of the position of
the pins 200 during an injection cycle according to a target
profile of pin positions that has been predetermined in advance for
the entire injection cycle as described more fully below.
[0114] Other valve and pin embodiments are usable in the invention.
A particularly suitable valve and pin design is described in U.S.
patent application publication no. 2002/0086086, published Jul. 4,
2002, the disclosure of which is incorporated herein by reference
in its entirety as if fully set forth herein. The pin and valve
design of this application show a pin having extended curvilinear
bulb upstream of the distal end of the pin. The bulb controls flow
rate upstream and away from the gate while the distal end of the
pin closes the gate in a manner analogous to the FIGS. 1, 4-6 valve
and pin embodiment described herein. FIGS. 32-34A of publication
no. 2002/0086086 illustrate flow stopped, flow enabled/controlled
and gate closed positions analogous to the positions and
configuration depicted in FIGS. 1, 4-6 herein.
[0115] Position sensors used in conjunction with the invention
typically comprise a mechanism that generates a signal that varies
according to the length, degree or amount of travel position of the
piston or flow controller to which the sensor is connected or
interacting with. Such continuously varying output sensors
typically generate an output that varies in degree of signal
strength such as voltage, amperage or the like. The sensors
described with reference to FIGS. 4, 4a, 7 are continuously varying
signal sensors. Alternatively, as described with reference to the
FIG. 4b embodiment, a sensor mechanism having a switch that
generates/provides an on or off signal (e.g. a toggle switch) can
be used in other embodiments of the invention where a sensor signal
that continuously varies in degree/strength is not feasible for use
in connection with a particular hotrunner/actuator arrangement.
[0116] FIG. 4a shows an alternative position sensing embodiment
wherein a magnetic or electromagnetic field is activated or sensed
by sensor 130 depending on the position of the piston 223 relative
to the position of mounting of the position sensor 130. As shown in
FIG. 4a, a window 132 is provided in the upper portion of the
piston housing which allows the magnetic or electromagnetic field
sensitive switch 130, shown mounted on the housing 225, to sense
the presence of the metal piston 223 through the window 132 when
the piston 223 is in a position relative to the window 132 that is
close enough to switch 130 to magnetically or electromagnetically
activate switch 130. When the piston 223 travels to a position that
is sufficiently clear of window 132, e.g to a position as shown in
FIG. 5, the switch 130 stops signaling or changes its signal
condition/content to controller 10 thus indicating that the piston
223 (and its associated pin 200) has traveled beyond a certain
predetermined limit position. FIG. 4b shows another position sensor
embodiment where the switch 130 comprises a mechanical, contact or
interference switch 130a having a mechanical contact member 133
that protrudes radially a slight distance through window 132.
Member 133 contacts piston 223 and switch 130a is activated when an
upper edge 223a or outer surface 223b of piston 223 travels to a
point that is longitudinally aligned with member 223 such that
mechanical contact is made with member 133.
[0117] In the FIGS. 4a, 4b embodiments, the switch 130, 130a and
the window 132 are arranged relative to each other such that switch
130 ceases sensing piston 223 or switch 130a loses contact with
piston 223 when the piston 223 and pin 200 have traveled to a
"limit position," i.e. a longitudinal position along the path of
travel of the piston where a portion of the piston 223 is not
aligned with window 132. When the switch 130, 130a ceases sensing
or making contact with the piston 223, the controller 10 receives a
signal from switch 130, 130a indicating that the switch is
deactivated or otherwise different from whatever signal, if any,
that the controller was previously receiving from switch 130, 130a
when the switch was sensing or in contact with piston 223. Thus the
controller 10 receives a signal indicative of the movement of the
pin 200 or piston 223 to a position at or beyond the predetermined
limit position. The limit position can be predetermined to be any
selected position of the pin or piston occurring within the time
interval of an injection cycle. In one embodiment, the limit
position of the pin/piston is selected to be a position as shown in
FIG. 5 where the pin is enabling fluid to flow at a maximum rate
and/or the fluid is at a maximum pressure within the time interval
of an injection cycle. As described below with reference to the
FIGS. 1, 4-6 embodiments when the controller 10 receives a signal
that the pin/piston has traveled to or beyond a selected limit
position such as a maximum flow position, the algorithm includes
instructions to direct movement of the pin in some predetermined
manner, such as to direct the pin to move back from a maximum flow
position to a position where the pin is in a range of pin positions
that control flow rate at a rate less than maximum flow or
otherwise where the fluid is not at maximum pressure. The detection
and signaling of the piston's reaching the limit position is
typically used by the controller 10 and in the control algorithm in
the same manner as described in detail below.
[0118] FIG. 7 shows an alternative position sensing embodiment
where an inductive position sensor 120 is mounted in a plate 122
that is mounted on the upper or rear surface of the housing 225 of
actuator 226. The inductive position sensor 120 senses the position
of travel of the piston 223 and its associated pin 200 by inductive
sensing of the position of a sensor target 110 mounted on the upper
or rear end 223a of piston 223. The position of travel or stroke
distance 112 of the piston 223 is thus detected by inductance
sensing and a signal 114 indicative of the position sensed can be
sent to the master controller 10 as shown in FIG. 7 and used in an
algorithm as described herein for controlling movement of the pin
200 according to the algorithm.
[0119] As shown in the FIG. 1 embodiment, the master computer or
controller 10 receives signal inputs indicative of a fluid material
condition from material condition sensors 217 and indicative of
position of the pin from sensors 100. The sensors 217 as shown in
FIG. 1 sense a condition of the fluid at a location or position
that are downstream of the location at which that portion of the
pins that control fluid flow rate are positioned. In the embodiment
shown, the pins have bulbous protrusions with outer surfaces 205
that control fluid flow rate by forming a gap with a complementary
inner surface of the flow channel. The condition sensors sense a
condition of the fluid at a location or position that are
downstream of the location at which fluid rate controlling surfaces
205 are positioned. As described below, in an embodiment where an
extended pin, FIGS. 1, 4-6 is used to both control flow rate and
shut off flow at the gate with the distal end of the pin, the use
of a position sensor 100 signal in combination with a condition
sensor signal to control flow rate during an injection cycle can
work to prevent the controller 10 from instructing the actuator 226
to move the pin beyond a limit of forward/downstream travel that
causes the distal end of the pin to prematurely close the gate and
stop flow during the course of an injection cycle.
[0120] FIGS. 1, 4-6 show a system in which control of material flow
is away from the gate. The embodiment shown utilizes an extended
valve pin design in which the valve pin closes the gate after
completion of material flow at the end of a cycle. The reverse
taper pin controllably varies flow rate during a cycle by use of a
reverse tapered control surface 205 for forming a gap 207 with a
surface 209 of the bushing 810 mounted in the manifold, FIGS. 4-6.
The action of displacing the pin 200 in an upstream direction
reduces the size of the gap 207, the maximum gap/flow position
shown in FIG. 6, an intermediate gap/flow position shown in FIG. 5
and a stop flow/closed gap position shown in FIG. 4. Consequently,
the rate of material flow through bores 208 and 214 of nozzle 215
and manifold 231, respectively, is reduced upon upstream movement
from the FIG. 6 position to the FIG. 4 position, thereby reducing
the pressure measured by the pressure transducer 217.
[0121] The valve pin 200 reciprocates by movement of piston 223
disposed in actuator body 225. This actuator is described in U.S.
Pat. No. 5,894,025 the disclosure of which is incorporated herein
by reference in its entirety. The use of this embodiment of an
actuator 226 enables easy access to valve pin 200 in that the
actuator body 225 and piston 223 can be removed from the manifold
and valve pin simply by releasing retaining ring 240.
[0122] Forward or downstream moving closure pins may also be used
in conjunction with the position sensing flow control apparatus and
method of the present invention. Such forward or downstream
movement pins are described in detail in U.S. Pat. No. 6,361,300.
In the forward closure method, the flow control gap between the
bulbous protrusion of the pin and the manifold (or nozzle) bore
surface decreases flow rate and pressure by forward movement with
complete closure occurring upon maximum forward movement as
described in U.S. Pat. No. 6,361,300. Algorithms can be included in
controller 10 for controlling pin (or ram/cylinder used in
conjuction with a shooting pot) position based on pin position
sensing in the same manner as described herein for the reverse
taper or upstream closure movement pin embodiments.
[0123] FIGS. 4-6 show the valve pin in three different positions.
FIG. 4 represents the position of the valve pin at the start of an
injection cycle. Generally, an injection cycle includes: 1) an
injection period during which substantial pressure is applied to
the melt stream from the injection molding machine to inject the
material in the mold cavity; 2) a reduction of the pressure from
the injection molding machine in which melt material is packed into
the mold cavity at a relatively constant pressure; and 3) a cooling
period in which the pressure decreases to zero and the article in
the mold solidifies. Just prior to the start of injection, tapered
control surface 205 is in contact with manifold bushing 810 surface
209 to prevent any material flow. At the start of injection the pin
200 will be opened to allow material flow. To start the injection
cycle the valve pin 200 is displaced downstream toward the gate to
permit material flow, as shown in FIG. 14. For applications where
flow rates through different gates during a single injection cycle
is different, not all the pins will be opened initially, for some
gates pin opening will be varied to sequence the fill into either a
single cavity or multiple cavities at different time and different
rates of flow. FIG. 6 shows the valve pin at the end of the
injection cycle after pack. The part is ejected from the mold while
the pin is in the position shown in FIG. 15.
[0124] Pin position is controlled by a controller 10 based on
position or pressure readings from one or both of sensors 100 or
217 that are fed to the controller 10. In a preferred embodiment,
the controller is a programmable controller, or "PLC," for example,
model number 90-30PLC manufactured by GE-Fanuc. The controller
compares the sensed position or pressure to a target position or
pressure and adjusts the position of the valve pin via servo valve
212 to track the target position or pressure, displacing the pin
forward toward the gate to increase material flow (and pressure)
and withdrawing the pin away from the gate to decrease material
flow (and pressure). In a preferred embodiment, the controller
performs this comparison and controls pin position according to a
PID algorithm.
[0125] The controller 10 performs these functions for all other
injection nozzles coupled to the manifold 231 during a single
injection cycle. Associated with each gate is a valve pin, rotary
valve, ram, cylinder or some type of flow control mechanism to
control the material flow rate. Also associated with each gate is
either or both of a position sensor and material condition sensor,
an input device for reading the output signal of the position
and/or condition sensor, an algorithm for signal comparison and PID
calculation (e.g., the controller 10), a program, memory and human
interface for setting, changing and storing a target profile (e.g.,
interface 214), an output circuit or program for sending
instruction signals to a servomechanism that is interconnected to
and drives the actuator that is interconnected to and drives the
pin, ram, rotary valve or the like that makes contact with the
fluid flow, and an actuator to move/drive the valve pin, ram,
cylinder, motor shaft or the like. The actuator can be
pneumatically, hydraulically or electrically driven. The foregoing
components associated with each gate to control the flow rate
through each nozzle comprise a control zone or axis of control.
Instead of a single controller used to control all control zones,
individual controllers can be used in a single control zone or
group of control zones.
[0126] An operator interface 214, for example, a personal computer,
is provided to store and input a particular target profile of
position or pressure or both into controller 10. Although a
personal computer is typically used, the interface 214 comprises
any appropriate graphical or alpha numeric display, and can be
mounted directly to the controller. As in previous embodiments, the
target position or pressure profile is selected for each gate
associated therewith by pre-determining the profile for each
injection cycle (typically including at least parameters for
injection position or pressure, injection time, pack position or
pressure and pack time), inputting the target profile into
controller 10, and running the process. In the case of a
multicavity application in which different parts are being produced
in independent cavities associated with each nozzle (a "family
tool" mold), it is preferable to create each target profile
separately, since differently shaped and sized cavities can have
different profiles which produce the parts. For example, in a
system having a manifold with four gates for injecting into four
separate cavities, to create a profile for a particular gate, three
of the four gates are shut off while the target profile is created
for the fourth. Three of the four nozzles are shut off by keeping
the valve pins in the position shown in FIG. 4 or 6 in which no
melt flow is permitted into the cavity.
[0127] To create a target profile for a particular gate, the
injection molding machine is set at maximum injection pressure and
screw speed, and parameters relating to the injection pressure or
injection pin/ram/valve position, injection time, pack pressure or
pack pin/ram/valve position, and pack time are set on the
controller 10 at values that the molder estimates will generate the
best parts based on part size, shape, material being used,
experience, etc. Multiple injection cycles are carried out on
atrial and error basis for each gate, with alterations being made
to the above parameters depending on the condition of the part
being produced during the trial cycle. When the most satisfactory
parts are produced, the profile that produced the most satisfactory
parts is determined for each gate and cavity associated therewith.
Preferably, the target profiles determined for each gate are stored
in a digital memory, e.g. on a file stored in interface 214 and
used by controller 10 for production. The process can then be run
under the control of the controller 10 for all gates using the
particularized profiles. The foregoing process of profile creation
can be used with any number of gates. Although it is preferable to
profile one gate and cavity at a time in a "family tool" mold
application (while the other gates or their associated valves are
closed), the target profiles can also be created by running all
nozzles simultaneously, and similarly adjusting each gate profile
according to the quality of the parts produced. This would be
preferable in an application where all the gates are injecting into
like cavities, since the profiles should be similar, if not the
same, for each gate and cavity associated therewith.
[0128] In single cavity applications (where multiple nozzles from a
manifold are injecting into a single cavity), the target profiles
would also be created by running the nozzles at the same time and
adjusting the profiles for each nozzle according to the quality of
the part being produced. The system can also be simplified without
using interface 214, in which each target profile can be stored on
a computer readable medium in controller 10, or the parameters can
be set manually on the controller.
[0129] The present invention can use any of the properties or
states that a selected sensor is capable of sensing as a basis for
creating a profile of target values for input as variables to an
algorithm to be executed by controller 10. In particular, a target
profile of the position of a valve pin, rotary valve or
ram/cylinder may be used such components being directly responsible
for controlling material flow. The values of other injection
machine, hotrunner or mold components or materials can also be used
to create a target profile that correlates to material flow. For
example, the position or condition of mechanical components or
drive materials associated with the direct flow control components
can be used where the condition or position of such associated
components/materials accurately corresponds to the position of the
direct flow control components. For example, the pressure or
temperature of the hydraulic or pneumatic fluid that drive a
servocontroller for an actuator can be used to create a target
profile. Similarly, the degree or state of electrical power/energy
consumption or output of an electrically powered motor that drives
the movement of a pin, valve or ram/cylinder can be used to create
a target profile indicative of position of the direct flow
controlling component.
[0130] In the FIGS. 1, 4-6 embodiments, position sensors 100 and
condition sensors 217 are shown as preferred for creating position
and/or material condition target profiles as well as for recording
and sending position and/or material condition data to the
controller 10 to be used in an algorithm that is designed to use
such data as a basis for instructing movement of the
servomechanisms that control movement of the direct flow control
components such as valve pin 200.
[0131] For purposes of ease of description, FIGS. 9a-d show sample
target profiles based solely on pressure recorded by sensors 217.
The X axis data of the profiles/graphs shown in FIG. 9a could
alternatively be position data that is generated by position
sensors 100.
[0132] As shown in FIGS. 9a-d, the graphs are material pressure
versus injection cycle time (235, 237, 239, 241) of the pressure
sensed by four pressure transducers associated with four nozzles
mounted in manifold block 231, FIG. 1 (only two nozzles shown). The
graphs of FIGS. 9a-d are generated on the user interface 214 so
that a user can observe the tracking of the actual pressure versus
the target pressure during the injection cycle in real time, or
after the cycle is complete. The four different graphs of FIG. 9a-d
show four independent target pressure profiles ("desired") emulated
by the four individual nozzles. Different target profiles are
desirable to uniformly fill different sized individual cavities
associated with each nozzle, or to uniformly fill different sized
sections of a single cavity.
[0133] The valve pin 200 associated with graph 235 is opened
sequentially at 0.5 seconds after the valves associated with the
other three graphs (237, 239 and 241) were opened at 0.00 seconds.
Referring back to FIGS. 4-6, just before opening, the valve pins
are in the position shown in FIG. 4, while at approximately 6.25
seconds at the end of the injection cycle all four valve pins are
in the position shown in FIG. 6. During injection (for example,
0.00 to 1.0 seconds in FIG. 9b) and pack (for example, 1.0 to 6.25
seconds in FIG. 9b) portions of the graphs, each valve pin is
instructed to move to a plurality of positions by controller 10 to
alter the pressure sensed by the pressure transducer 217 associated
therewith to track the target pressures of FIGS. 9a-d.
[0134] Through the user interface 214, target profiles can be
designed, and changes can be made to any of the target profiles
using standard windows-based editing techniques. The profiles are
then used by controller 10 to control the position of the valve
pins 200. For example, FIG. 10 shows an example of a profile
creation and editing screen icon 300 generated on interface 214.
Screen icon 300 is generated by a windows-based application
performed on interface 214. Alternatively, this icon could be
generated on an interface associated with controller 10. Screen
icon 300 provides a user with the ability to create a new target
profile or edit an existing target profile for any given nozzle and
cavity associated therewith. Screen icon 300 and the profile
creation text techniques described herein are described with
reference to FIGS. 4-6, although they are applicable to all
embodiments described herein.
[0135] In the pressure based profiles of FIGS. 9a-d a profile 310
includes (x, y) data pairs, corresponding to time values 320 and
pressure values 330 which represent the desired pressure sensed by
the pressure transducer for the particular nozzle being profiled.
The screen icon shown in FIG. 10 is shown in a "basic" mode in
which a limited group of parameters are entered to generate a
profile. For example, in the foregoing embodiment, the "basic" mode
permits a user to input start time displayed at 340, maximum fill
pressure displayed at 350 (also known as injection pressure), the
start of pack time displayed at 360, the pack pressure displayed at
370, and the total cycle time displayed at 380. The screen also
allows the user to select the particular valve pin they are
controlling displayed at 390, and name the part being molded
displayed at 400. Each of these parameters can be adjusted
independently using standard windows-based editing techniques such
as using a cursor to actuate up/down arrows 410, or by simply
typing in values on a keyboard. As these parameters are entered and
modified, the profile will be displayed on a graph 420 according to
the parameters selected at that time.
[0136] By clicking on a pull-down menu arrow 391, the user can
select different nozzle valves in order to create, view or edit a
profile for the selected nozzle valve and cavity associated
therewith. Also, a part name 400 can be entered and displayed for
each selected nozzle valve. The newly edited profile can be saved
in computer memory individually, or saved as a group of profiles
for a group of nozzles that inject into a particular single or
multi-cavity mold. The term "recipe" is used to describe a group of
profiles for a particular mold and the name of the particular
recipe is displayed at 430 on the screen icon.
[0137] To create a new profile or edit an existing profile, first
the user selects a particular nozzle valve of the group of valves
for the particular recipe group being profiled. The valve selection
is displayed at 390. The user inputs an alpha/numeric name to be
associated with the profile being created, for family tool molds
this may be called a part name displayed at 400. The user then
inputs a time displayed at 340 to specify when injection starts. A
delay can be with particular valve pins to sequence the opening of
the valve pins and the injection of melt material into different
gates of a mold. The user then inputs the fill (injection) pressure
displayed at 350. In the basic mode, the ramp from zero pressure to
max fill pressure is a fixed time, for example, 0.3 seconds. The
user next inputs the start pack time to indicate when the pack
phase of the injection cycle starts. The ramp from the filling
phase to the packing phase is also fixed time in the basic mode,
for example, 0.3 seconds.
[0138] The final parameter is the cycle time which is displayed at
380 in which the user specifies when the pack phase (and the
injection cycle) ends. The ramp from the pack phase to zero
pressure will be instantaneous when a valve pin is used to close
the gate, as in the embodiment of FIG. 4 due to the residual
pressure in the cavity which will decay to zero pressure once the
part solidifies in the mold cavity. User input buttons 415 through
455 are used to save and load target profiles. Button 415 permits
the user to close the screen. When this button is clicked, the
current group of profiles will take effect for the recipe being
profiled. Cancel button 425 is used to ignore current profile
changes and revert back to the original profiles and close the
screen. Read Trace button 435 is used to load an existing and saved
target profile from memory. The profiles can be stored in memory
contained in the interface 215 or the controller 10. Save trace
button 440 is used to save the current profile. Read group button
445 is used to load an existing recipe group. Save group button 450
is used to save the current group of target profiles for a group of
nozzle valve pins. The process tuning button 455 allows the user to
change the PID settings (for example, the gains) for a particular
nozzle valve in a control zone. Also displayed is a pressure range
465 for the injection molding application.
[0139] Button 460 permits the user to toggle to an "advanced" mode
profile creation and editing screen. The advanced profile creation
and editing screen is shown in FIG. 11. The advanced mode allows a
greater number of profile points to be inserted, edited, or deleted
than the basic mode. As in the basic mode, as the profile is
changed, the resulting profile is displayed. The advanced mode
offers greater profitability because the user can select values for
individual time and pressure data pairs. As shown in the graph 420,
the profile 470 displayed is not limited to a single pressure for
fill and pack, respectively, as in the basic mode. In the advanced
mode, individual (x, y) data pairs (time and pressure) can be
selected anywhere during the injection cycle. To create and edit a
profile using advanced mode, the user can select a plurality of
times during the injection cycle (for example 16 different times),
and select a pressure value for each selected time. Using standard
windows-based editing techniques (arrows 475) the user assigns
consecutive points along the profile (displayed at 478), particular
time values displayed at 480 and particular pressure values
displayed at 485. The next button 490 is used to select the next
point on the profile for editing. Prev button 495 is used to select
the previous point on the profile for editing. Delete button 500 is
used for deleting the currently selected point. When the delete
button is used the two adjacent points will be redrawn showing one
straight line segment. The add button 510 is used to add a new
point after the currently selected point in which time and pressure
values are entered for the new point. When the add button is used
the two adjacent points will be redrawn showing two segments
connecting to the new point.
[0140] FIG. 8 shows an example of an algorithm executable by
controller 10 using both pressure and pin position as variables for
control of movement of an extended pin 200 such as shown in FIGS.
4-6. Such an algorithm is useful particularly where material
condition measurement by a sensor such as pressure sensor 217 is
not alone sufficient to precisely base control on. For example, as
shown in FIG. 5, the pin is in a position where material flow is
occurring during the injection and/or pack stages of the injection
cycle. As described above, when the target profile calls for an
increase in pressure or a change in position to increase material
flow, the controller 10 will cause the valve pin 200 to move
forward to increase gap 207, which increases material flow and the
pressure sensed by pressure transducer 217. However, if the
injection molding machine is not providing adequate pressure to
meet the higher pressure called for by the target pressure, moving
the pin 200 forward beyond the position shown in FIG. 5 will not
increase the pressure sensed by transducer 217 enough to reach the
target pressure and the controller 10 will continue to instruct the
servomechanism 212 to move the pin forward. This could lead to a
loss of control since moving the pin further forward will tend to
cause the distal end or head 227 of the valve pin 200 to
prematurely move to the position shown in FIG. 6 and close the gate
211.
[0141] The controller 10 may also not correctly instruct the
servomechanism 212 due to a time delay in the increase of pressure
at the position of sensor 217 and thus a delay in the accuracy of
data being recorded by pressure sensor 217 relative to the assumed
instantaneous pressure increase on which the target profile of time
versus pressure is based. Such discrepancy in sensor measurement
can occur as a result of a gradient in material pressure between
bore 208, 213 and pressure in the machine barrel or channel 13, the
delay in pressure increase resulting in the controller 10
instructing the pin 200 to move further downstream than desired,
possibly to a point where the distal end 227 of the pin 200 begins
to restrict flow at the gate 211 or stops flow altogether.
[0142] Accordingly, to maintain precise control of the pin 200
according to the predetermined pressure versus time profile, the
controller is programmed with an algorithm according to the flow
chart of FIG. 8 where a predetermined limit position is selected,
the limit position typically being a position at which maximum flow
or pressure occurs. In practice, the extended pin 200 embodiment
has a plurality of maximum flow/pressure positions extending over a
length of travel somewhere between the closed position shown in
FIG. 6 and the position shown in FIG. 5. The limit position is
typically selected as being one or more of the maximum
flow/pressure positions, however another position can be selected
as the limit position, if desired, for particular processing
reasons peculiar to the part being produced.
[0143] As shown in FIG. 8, the algorithm executed by controller 10
includes instructions that compare the signal being received from
position sensor 100 with the limit position to determine first
whether the pin is at the limit position at a time prior to the end
of the injection and pack phases of the cycle and, if so, the
controller 10 then compares the pressure signal from sensor 217 to
the profile pressure at the same point in time to determine whether
an increase or decrease in pressure is called for by the profile.
If the profile calls for a decrease in pressure at the point where
the pin is at the limit position, controller 10 reverts to control
of the pin 200 according to the pressure profile, i.e. upstream
movement to decrease pressure according to the pressure profile. If
the profile calls for an increase in pressure when the pin is at
the limit position, the controller 10 sends instructions to the
servomechanism 212 to either maintain the pin at its limit position
or slightly decrease the pressure (i.e. move the pin upstream)
until such time as the profile calls for a decrease in pressure
along the course of time of the cycle, i.e. along the length of the
Y axis of FIGS. 9a-d. Preferably, if the position sensor 100
signals that the pin 200 has traveled beyond the limit position,
the controller algorithm includes instructions to direct the
servomechanism to halt or reverse pin travel slightly.
[0144] As described above the position sensor 100 typically
comprises a variable resistor or potentiometer that outputs a
voltage signal that varies depending on the degree of extension of
rod 102. Also as described above, the sensor embodiment 130 of FIG.
4a can be used to detect/sense travel of the pin 200 to or beyond
the limit position and signal the controller 10. Other sensors such
as a linear voltage differential transformer (LVDT) 100 can be
coupled to the pin shaft 200 as shown in FIGS. 2, 3, to produce an
output signal proportional to the distance that pin 200 or piston
223 travels. Similarly, the inductive position sensor apparatus
112, 120 and its associated components, FIG. 7 can be used to
sense, record and signal pin or piston position to the controller
10. A sensor that operates via a variation in capacitance, i.e. a
capacitative sensor, can be coupled to the piston 223 or pin 200.
Where an electronic or electrically powered actuator is used to
move the pin instead of the hydraulic or pneumatic actuators shown
in FIGS. 1-7, the output signal to the electric motor or the
servo-control to the motor can be used to estimate pin position, or
an encoder mechanism can be interconnected to the motor to generate
an output signal proportional to pin position.
[0145] At the end of the pack portion of the injection cycle, the
valve pin 200 is instructed by the algorithm to move all the way
forward/downstream to close off the gate as shown in FIG. 6. In the
foregoing example, the full stroke of the pin (from the position in
FIG. 4 to the position in FIG. 6) is relatively small, e.g. 12
millimeters, and the rate of flow control stroke length is a
fraction of the total, e.g. 4 millimeters. The algorithm instructs
the pin 200 to keep the gate 211 closed until just prior to the
start of the next injection cycle when it is opened and pin 200 is
moved to the position shown in FIG. 4. Immediately after the start
of the next cycle, the pin 200 is instructed to move to the limit
position as shown in FIG. 8. While the gate 211 is closed, as shown
in FIG. 6, the injection molding machine begins plastication for
the start of the next injection cycle as the part is cooled and
ejected from the mold.
[0146] FIGS. 12-18 show an alternative embodiment of the invention
in which a "forward" shutoff is used rather than a retracted
shutoff as shown in FIGS. 1-5. In the embodiment of FIGS. 12 and
13, the forward cone-shaped tapered portion 1195 of the valve pin
head 1143 is used to control the flow of melt with surface 1197 of
the inner bore 1120 of nozzle 1123. An advantage of this
arrangement is that the valve pin stem 1102 does not restrict the
flow of melt as in FIGS. 1-5. As seen in FIGS. 1-5, the clearance
between the stem and the bore of the manifold is not as great as
the clearance 1198 in FIGS. 12 and 13. The increased clearance 98
in FIGS. 12-13 results in a lesser pressure drop and less shear on
the plastic.
[0147] In FIGS. 12 and 13 the control gap 1198 is formed by the
front cone-shaped portion 1195 and the surface 1197 of the bore
1120 of the rear end of the nozzle 1123. The pressure transducer
1169 is located downstream of the control gap--thus, in FIGS. 12
and 13, the nozzle is machined to accommodate the pressure
transducer as opposed to the pressure transducer being mounted in
the manifold as in FIGS. 1-5.
[0148] FIG. 13 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
1137 of the bore 1120 of the nozzle which reduces the width of the
control gap 1198. To increase the flow of melt the valve pin is
retracted to increase the size of the gap 1198.
[0149] The rear 1145 of the valve pin head 1143 remains tapered at
an angle from the stem 1102 of the valve pin 1141. Although the
surface 1145 performs no sealing function in this embodiment, it is
still tapered from the stem to facilitate even melt flow and reduce
dead spots.
[0150] As in FIGS. 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 1141 to follow a target
pressure profile. The forward shut-off arrangement shown in FIGS.
12 and 13 also has the advantages of the embodiment shown in FIGS.
1-5 in that a large valve pin head 1143 is used to create a long
control gap 1198 and a large control surface 1197. As stated above,
a longer control gap and greater control surface provides more
precise control of the pressure and melt flow rate.
[0151] FIGS. 14 and 15 show a forward shutoff arrangement similar
to FIGS. 12 and 13, but instead of shutting off at the rear of the
nozzle 1123, the shut-off is located in the manifold at surface
1101. Thus, in the embodiment shown in FIGS. 14 and 15, a
conventional threaded nozzle 1123 may be used with a manifold 1115,
since the manifold is machined to accommodate the pressure
transducer 1169 as in FIGS. 1-5. A spacer 1188 is provided to
insulate the manifold from the mold. This embodiment also includes
a plug 1187 for easy removal of the valve pin head 1143. The plug
1187 is inserted in the manifold 1115 and held in place by a cap
1189. A dowel 1186 keeps the plug from rotating in the recess of
the manifold that the plug is mounted. The plug has a bore through
which a stem of the valve pin of the nozzle passes.
[0152] FIG. 16 shows an alternative embodiment of the invention in
which a forward shutoff valve pin head is shown as used in FIGS.
12-15. However, in this embodiment, the forward cone-shaped taper
1195 on the valve pin includes a raised section 1103 and a recessed
section 1104. Ridge 1105 shows where the raised portion begins and
the recessed section ends. Thus, a gap 1107 remains between the
bore 1120 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 1109 is used to seal and
close the valve pin. The gap 1107 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. When injection begins melt will flow into gap
1107 and provide a force component F1 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.
[0153] Despite the fact that the gap 1107 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 FIGS. 1-5,
12-15.
[0154] FIGS. 17 and 18 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
1169 and PID control system is the same as in previous embodiments.
In this embodiment, however, the valve pin 1141 extends past the
area of flow control via extension 1110 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 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 1112 of the valve pin 1141.
[0155] 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.
[0156] The flow control area is shown enlarged in FIG. 18. 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 1114 that tapers from edge 1128 of the stem 1102 of the
valve pin 1141 to a throat area 1116 of reduced diameter. From
throat area 1116, the valve pin expands in diameter in section 1118
to the extension 1110 which extends in a uniform diameter to the
tapered end of the valve pin.
[0157] 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 1122. From the section of
reduced diameter the manifold channel then expands in diameter in a
section defined by surface 1124 to an outlet of the manifold 126
that communicates with the bore of the nozzle 20. FIGS. 1117 and
1118 show the support ring style nozzle similar to FIGS. 1-3.
However, other types of nozzles may be used such as, for example, a
threaded nozzle as shown in FIG. 14.
[0158] As stated above, the valve pin is shown in the fully opened
position in solid lines. In FIG. 18, flow control is achieved and
melt flow reduced by moving the valve pin 1141 forward toward the
gate thereby reducing the width of the control gap 1198. Thus,
surface 1114 approaches surface 1120 of the manifold to reduce the
width of the control gap and reduce the rate of melt flow through
the manifold to the gate.
[0159] To prevent melt flow from the manifold bore 1119, and end
the injection cycle, the valve pin is moved forward so that edge
1128 of the valve pin, i.e., where the stem 1102 meets the
beginning of curved surface 1114, will move past point 1130 which
is the beginning of surface 1122 that defines the section of
reduced diameter of the manifold bore 1119. When edge 1128 extends
past point 1130 of the manifold bore melt flow is prevented since
the surface of the valve stem 1102 seals with surface 1122 of the
manifold. The valve pin is shown in dashed lines where edge 1128 is
forward enough to form a seal with surface 1122. 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 1102 moving further along, and continuing to seal with,
surface 1122 of the manifold until the end 1112 of the valve pin
closes with the gate.
[0160] In this way, the valve pin does not need to be machined to
close the gate and the flow bore 1119 of the manifold
simultaneously, since stem 1102 forms a seal with surface 1122
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 1112 of the valve pin will
not interfere with melt flow, since once the valve pin is retracted
enough to permit melt flow through gap 1198, the valve pin end 1112
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 stein 1102 and surface 1122, and another 6
mm. to close the gate. Thus, the valve pin would have 1112 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.
[0161] FIG. 19 shows a valve pin 700 having a smooth outer surfaced
curvilinear bulbous protrusion 750 for controlling melt flow from
manifold channel 760 to nozzle channel 710. The pin 700 is slidably
mounted in nozzle channel 710 having a distal extension section 720
having a tip end 730 for closing off gate 740 when the pin is
appropriately driven to the position shown in FIG. 16. The pin 700,
830 is controllably slidable along its axis Z. The bulbous
protrusion 750 as shown in FIGS. 14, 14A is in a flow shut-off
position where the outer surface of a maximum diameter section 755
of the bulb makes engagement contact with a complementary shaped
interior surface of the channel 765 sufficient to prevent melt flow
770 from passing through the throat section 766 where and when the
bulb surface 755 engages the inner surface 765 of the flow channel.
As perhaps best shown in FIG. 21, the bulb 750 has an intermediate
maximum diameter section which is intermediate an upstream smooth
curvilinear surfaced portion 820a and a downstream smooth
curvilinear surfaced portion 810a. Melt flow 900 flowing under
pressure from manifold or hotrunner channel 770 toward nozzle
channel 710 passes through flow controlling passage 767. The melt
flow is slower the narrower passage 767 is and faster the wider
that passage 767 is. Passage 767 may be controllably made narrower
or wider by controlled CPU operation of actuator 790 as described
above with reference to other embodiments via an algorithm which
receives sensor variable signals from a sensor such as sensor 780.
In the FIGS. 19-26 embodiments, the passage 767 is gradually made
wider and flow increased by downstream movement of the bulb 750
toward the gate 740. By contrast, in the FIG. 27 embodiment, the
passage 767 is made narrower by downstream movement of the bulb 750
from the position shown in FIG. 27 toward the throat 766
restriction section, and made wider by upstream movement of the
bulb 750 away from the gate 740.
[0162] As shown in FIG. 26, the maximum diameter section typically
has a straight surface 755 forming a cylindrical surface on the
exterior of the bulb 750 having a diameter X. The throat 766 has a
complementary straight interior surface 765 in the form of a
cylinder having the same diameter X as the surface 755. Thus as the
bulb 750 is moved in an upstream direction (away from the gate)
from the position shown in FIG. 26, the flow controlling
restriction 767 gets narrower and the melt flow 900 is gradually
slowed until the surface 755 comes into engagement with surface 765
at which point flow is stopped at the throat 766. The same sequence
of operation events occurs with respect to all of the embodiments
shown in FIGS. 19-26. The maximum diameter surface 755 does not
necessarily need to be cylindrical in shape. Surface 755 could be a
finite circle which mates with a complementary diametrical circle
on mating surface 765. The precise shape of surface 755 may be
other than circular or round; such surface 755 could alternatively
be square, triangular, rectangular, hexagonal or the like in
cross-section and its mating surface 765 could be complementary in
shape.
[0163] FIGS. 21, 21A show a third position where the end of the
extended pin closes off flow through gate 740. FIGS. 19, 19A show a
position where flow 900 is shutoff at throat 766. FIGS. 20, 20A
show a pin/bulb position where flow 900 is being controlled to flow
at a preselected rate. Any one or more positions where the bulb
surface 755 is further or closer to surface 765 may be controllably
selected by the CPU according to the algorithm resident in the CPU,
the flow rate varying according to the precise position of the bulb
surface 755 relative to the mating surface 765.
[0164] FIGS. 22, 23 show an embodiment where the pin does not have
a distal end extension for closing off the gate 740 as the FIGS.
19-21 embodiment may accomplish. In such an embodiment, the
algorithm for controlling flow does not have a third position for
closing the gate 740.
[0165] FIGS. 24, 25A and 27 show an embodiment where the
longitudinal aperture 800 in which the pin 830 is slidably mounted
in bushing or mount 810 has the same or a larger diameter than the
maximum diameter surface 755 of bulb 750. The aperture 800 extends
through the body or housing of heated manifold or hotrunner 820 and
thus allows pin 830 to be completely removed by backwards or
upstream withdrawal 832, FIG. 24A, out of the top end of actuator
790 for pin replacement purposes without the necessity of having to
remove mount or bushing 810 in order to replace/remove pin 830 when
a breakage of pin 830 may occur. The bushing or mount 810 is
typically press fit into a complementary mounting aperture 850
provided in the body or housing of manifold or hotrunner 820 such
that a fluid seal is formed between the outer surface of bushing or
mount 810 and aperture 850. The central slide aperture for pin 830
extends the length of the axis of actuator 790 such that pin 830
may be manually withdrawn from the top end of actuator 790.
[0166] As described above, the slidable back and forth movement of
a pin 830 having a bulb 750, FIGS. 19-27, is controllable via an
algorithm residing in CPU or computer, FIG. 22 which receives one
or more variable inputs from one or more sensors 780.
[0167] The melt flow 900 is readily controllable from upstream
channel 770 to downstream 710 channel by virtue of the ready and
smooth travel of the melt over first the upstream smooth
curvilinear surface 820a past the maximum diameter surface 755 and
then over the smooth downstream curvilinear surface 810a. Such
smooth surfaces provide better control over the rate at which flow
is slowed by restricting passage 767 or speeded up by making
passage 767 wider as pin 830 is controllably moved up and down. The
inner surface 765 of throat section 766 is configured to allow
maximum diameter surface 755 to fit within throat 766 upon back and
forth movement of bulb 750 through throat 766.
[0168] FIGS. 28-32 show an alternative embodiment in which a load
cell 1140 is used to sense the melt pressure acting on the face
1142 of valve pin 1041. Where possible, reference characters are
used that refer to elements common to FIG. 1. As in previous
embodiments, an actuator 1049 is used to translate the valve pin
1041 toward and away from the gate. The actuator 1049 includes a
housing 1144 and a piston 1146 slidably mounted within the housing.
The actuator is fed by pneumatic or hydraulic lines 1148 and 1150.
Other actuators, for example, electrical actuators may also be
used.
[0169] The valve pin 1041 is mounted to the piston 1146 so that
valve pin translates through the injection nozzle 1023 with
movement of the piston. The valve pin is mounted to the piston via
a pin 1152. The pin 1152 is slotted so that a clearance 1154 exists
in which the valve pin can translate with respect to the pin 1152
and piston 1146. The valve pin bears against a button 1156 on the
load cell 1140. The load cell 1140 is mounted via screws 1158 to
the piston. Thus, as shown in FIG. 31B, a force F.sub.2 acting on
the valve pin will cause the load button 1156 to depress.
Excitation voltages or other types of signals which indicate the
proportionate force on the load button 1156 are carried through
cable 1160 and fed to a controller 1151.
[0170] In operation, as seen in FIG. 28, the melt material is
injected from an injection molding machine nozzle 1011 into an
extended inlet 1013 mounted to a manifold 1015 through respective
injection molding nozzles 1021 and 1023 and into mold cavities 1162
and 1164. In the embodiment shown, a multi-cavity mold is shown in
which nozzles 1021 and 1023 inject melt material to form different
size molded parts in cavities 1162 and 1164, respectively. As
stated above, a mold cavity with multiple gates can be used, or
multiple mold cavities with cavities having the same size can be
used.
[0171] When the valve pin 1041 is retracted to permit melt material
to be injected into the cavity 1162, the melt pressure will act on
the face of the valve pin 1142 with the resulting force being
transmitted through the shaft of the valve pin to the load sensor
1140 (see FIGS. 30-31). Thus, the load (F.sub.2) sensed by load
cell 1140 is directly related to the melt flow rate into the melt
cavity.
[0172] Sheer stresses caused by the melt streaming downward over
the valve pin will tend to reduce the pressure sensed by the load
cell but such stresses are typically less than the nominal load due
to the melt pressure. Thus, the resultant force F.sub.2 will tend
to compress the valve pin toward the load cell, with the possible
exception of the initial opening of the valve, and the load cell
provides an accurate indicator of the melt pressure at the gate. If
the application results in sheer stresses exceeding F.sub.2, the
load cell can be pre-loaded to compensate for such stresses.
[0173] Similar to previous embodiments described above, the signal
transmitted through cable 1160 is compared by controller 1151 with
a target value of a target profile and the controller adjusts the
position of the valve pin accordingly to increase or decrease flow
rate. In this embodiment, the target profile is also a time versus
pressure profile, but the pressure is the a result of the force of
the pin on the load cell, as opposed to previous embodiments in
which a pressure transducer directly senses the force of the flow
of the melt material. The profile is created in similar fashion to
the embodiments described above: running the process and adjusting
the profile until acceptable parts are produced.
[0174] The valve pin controls the flow rate through the gate using
a tapered edge 1155 to form a control gap 1153 close to the gate.
It should be noted, however, that any of the other valve pin
designs described herein can be used with the load cell 1140.
Accordingly, when the pressure sensed by the load cell is less than
the target pressure on the target profile, the controller 1151
signals the actuator to retract the valve pin to increase the size
of the control gap 1153 and, consequently, the flow rate. If the
pressure sensed by the load cell 1140 is greater than the target
pressure, the controller 1151 signals the actuator to displace the
valve pin toward the gate to decrease the size of the control gap
1153 and consequently, the flow rate.
[0175] The use of the load cell has an additional application shown
in FIG. 31A. In a single cavity multiple gate system it is often
desirable to open gates in a cascading fashion as soon as the flow
front of the melt material reaches the gate. When melt material
1166 has flowed into the gate area of the valve pin, a force
F.sub.2 from the melt in the cavity is exerted on the face 1142 of
the valve pin.
[0176] In this way, gates can be sequentially opened in cascading
fashion by sensing the force of the melt pressure on the face of
the valve pin when the valve pin is closed. Given typical gate
diameters of 0.2 inches and melt pressures of 10,000 psi, the
resulting force of 300 pounds is readily measured by available load
sensors, since the force of the cell equals the area of the gate
times the pressure at the gate. Thus, this melt detection can then
be used to signal the opening of the gate as in the sequential
valve gate. This assures that the gate does not open
prematurely.
[0177] FIGS. 32A and 32B show an alternative embodiment in which
the sheer stress on the valve pin is reduced. The nozzle 1021 is
designed to include a channel for melt flow 1168 and a bore 1170
through which the valve pin reciprocates. As such, the flow does
not cause any axial sheer stress on the valve pin and thus reduces
errors in pressure sensing. An indent 1172 is provided in the
nozzle 1021 so that side load on the valve pin is reduced, i.e., to
equalize pressure on both sides of the valve pin. An additional
benefit to the configuration shown in FIGS. 32A and 32B is that
since the flow of material is away from the valve pin, the valve
pin does not "split" the flow of material, which can tend to cause
part lines or a flow streak on the molded part.
[0178] FIG. 33 shows another alternative embodiment of the present
invention in which a ram 1565 is used to force material from well
1640 into cavity 1525 at a controlled rate. The rate is controlled
by signals sent from controller 1535 to servo valve 1560A, which in
turn controls the velocity at which actuator 1560 moves ram 1565
forward.
[0179] In FIG. 33, actuator 1560 is shown in more detail including
piston 1564, actuator chamber 1566, and hydraulic lines 1561 and
1562 controlled by servo valve 1560A. Energizing hydraulic line
1561 and filling chamber 1566 causes piston 1564 and ram 1565 to
move forward and displace material from well 1640 through channel
1585 and nozzle 1520, and into cavity 1525.
[0180] Accordingly, as in previous embodiments, a target profile is
created that has been demonstrated to generate acceptable molded
parts. In the embodiment of FIG. 33, however, the target profile
represents target values of the hydraulic pressure sensed by
pressure transducer 1563, as opposed to directly sensing the
material pressure. In operation, the controller compares the
pressure signal sensed from pressure transducer 1563 to the target
pressure profile for gate 1555. If the pressure sensed is too low,
the controller will increase the hydraulic pressure in line 1561
(which increases the velocity of the ram which increases flow rate
of the material), if the pressure is too high the controller will
decrease the hydraulic pressure (which decreases the velocity of
the ram which decreases the rate of material flow).
[0181] The target pressure profile of the hydraulic fluid will
appear similar to a conventional material profile, since the
pressure of the hydraulic fluid will rise rapidly during the
injection portion of the cycle, level off during the pack portion
of the cycle, and go to zero pressure as cycle ends the valve pin
1550 closes.
[0182] Although only one injection nozzle 1520 and cavity 1525 is
shown, there is a like arrangement associated with each injection
nozzle of actuators 1575, 1565, 1545, as well as solenoid valves
1540 and 1570 and servo valve 1560, to independently control the
melt flowing from each gate, according to the target profile
created for that gate. Also, although a single cavity 1525 is
shown, each nozzle may inject to multiple cavities or a single
cavity mold. Only a single controller 1535, however, is needed to
control all the nozzles associated with manifold 1515.
[0183] Using the foregoing arrangement of FIG. 33, as in previous
embodiments, the material flow from each nozzle of the manifold can
be controlled independently.
[0184] FIG. 34 shows another alternative embodiment of the present
invention. The embodiment of FIG. 34 is substantially the same as
the embodiment shown in FIGS. 1, 5-6 with the exception that
pressure transducer 1217 has been moved from manifold 1231 to
inside the mold half 1650 which, together with mold half 1660,
forms mold cavity 1670 in which the molded part is formed.
Accordingly, in this embodiment, the target profile represents
target values of the pressure sensed by pressure transducer 1217
inside the cavity opposite the gate 1211.
[0185] The operation of the embodiment of FIG. 34 is the same as
that described in the embodiment shown in FIG. 5 in terms of target
profile creation and use of valve pin 1200 to control the material
flow (interface 1214 is not shown but can be used). However,
placing the pressure transducer in the cavity offers several
advantages, for example, in the cavity the pressure transducer 1217
is not exposed to the high temperatures generated by the manifold,
as in FIG. 5. Also, the presence of the pressure transducer in the
manifold may slightly disrupt material flow in the manifold.
Another consideration in choosing whether to mount the transducer
in the mold or in the manifold is whether the mold geometry permits
the transducer to be mounted in the mold.
[0186] FIG. 35 is another alternative embodiment of the present
invention that is similar to FIG. 5. Target profile creation as
well as the flow control operation by valve pin 2000 is
substantially the same as described above. FIG. 35, however, does
not include a pressure transducer 217 as shown in FIG. 5 to
directly sense the flow of melt material into the cavity. Rather,
similar to the embodiment shown in FIG. 33, the arrangement shown
in FIG. 35 performs flow control by sensing the material pressure
F.sub.2 exerted by the melt material on the valve pin.
[0187] In FIG. 28 measuring the load on the valve pin was performed
using a load cell 1140, however, in FIG. 35, it is performed by
pressure transducers 1700 and 1710 mounted along hydraulic lines
1720 and 1730 which lead to actuator chambers 1740 and 1750,
respectively. Energizing lines 1720 and 1730 and filling actuator
chambers 1740 and 1750, enables axial movement of piston 1223,
thereby moving valve pin 1200 and affecting the flow rate of the
material into the cavity 1760 as described above.
[0188] Pressure transducers 1700 and 1710 sense a differential
pressure which is directly related to the force exerted on valve
pin 1200, which is directly related to the flow rate of the
material. For example, when the material flow causes a force
F.sub.2 to act on valve pin 1200, the force relates up the valve
pin to the piston, which in turn tends to increase the pressure in
chamber 1740 and line 1720 and decrease the pressure in chamber
1750 and line 1730, directly causing a change in the difference in
the pressures sensed by the transducers 1700 and 1710. Accordingly,
the differential pressure is directly related to the flow rate of
the material into the cavity.
[0189] Once an acceptable target profile of differential pressure
is developed using techniques described above, the controller will
cause the servo valve 1212 to track this target profile by altering
the position of the valve pin to change the flow rate of the
material and track the differential pressure target profile. For
example, if the differential pressure is too high (e.g., the
pressure sensed by transducer 1700 is higher than the pressure
sensed by transducer 1710 by an amount greater than the target
differential pressure) the controller will cause servo valve to
retract the valve pin to reduce the flow rate, thereby reducing the
force F.sub.2 on the valve pin, thereby decreasing the pressure in
chamber 1740 and line 1720, thereby decreasing the pressure sensed
by transducer 1700, thereby decreasing the difference in pressure
sensed by transducers 1700 and 1710. Note, in certain applications
the differential pressure may be negative due to the sheer force of
the material on the valve pin, this however will not affect the
controller's ability to track the target profile.
[0190] As in the embodiment shown in FIG. 28, the embodiment shown
in FIG. 35 offers the advantage that it is not necessary to mount a
pressure transducer in the mold or the manifold. As in all previous
embodiments, the embodiment shown in FIG. 35 enables the material
flow from each nozzle attached to the manifold to be independently
profileable.
[0191] With reference to FIGS. 2a, 2b, an electrically driven motor
drives a pin 50 along its axis without rotation as follows. The pin
50 has an pin head 52 interconnected via coupling components 51, 56
to a screw 72 which is screwably engaged within a complementary nut
aperture within nut coupling component 56. As shown, the pin head
52 is interconnected to screw 72 outside the hot runner manifold 75
and the pin is slidably mounted in a complementary receiving
aperture 90 within the manifold housing 75 such that the pin 50 is
disposed within melt channel 20 for slidable movement along pin
axis X which in the embodiment shown is coaxial with motor shaft
60. Nut component 56 is attached to coupling component 51 via
bolting between apertures 59 as best shown in FIG. 5b.
[0192] As best shown in FIG. 5b, nut component 56 has slots 82 into
which keys 84 provided on mounting housing 58 slide so as to render
nut component 56 non-rotatable with respect to coupling component
51, pin 50, housing 58 and motor housing 64.
[0193] The rotatably driven shaft 60, FIGS. 2b, 5b of the motor
(not shown) housed within housing 64 is coaxially aligned along
axis X with screw 72 and pin 50 and is engaged with the top end of
screw 72 such that when shaft 60 rotates screw 72 simultaneously
rotates. As screw 72 rotates, nut 56 travels along axis X. Through
the coupled interconnection of the end 52 of pin 50 with nut 56,
pin 50 is simultaneously driven and travels along axis X together
with the travel of nut 56 which thus acts together with screw 72 as
an actuating mechanism for pin 50. As shown in FIGS. 2b, 4a, 5b, a
load cell 54 may be included. As shown, the load cell is coupled to
pin end 52 such that the pressure sensitive surface of the load
cell 54 is snugly engaged with the top end surface of the end 52 of
pin 50 such that axial force along axis X to which pin 50 is
subject is sensed by load cell 54. In this embodiment, the force or
pressure measured by the load cell 54 is preferably input as a
value into a PID and/or other CPU program which controls the drive
of the shaft 60 of the motor housed within 64. As shown in FIG. 2b
a thrust bearing is mounted between shaft 60 and the housing 58 for
screw 72/nut 56 so as to absorb axial force transmitted from pin 50
to nut 56 and screw 72 and thus substantially reduce and/or
eliminate load on the shaft 60 of the motor along axis X. Such
axial load would otherwise be transmitted to shaft 60 as a result
of engagement of shaft 60 with screw 72.
[0194] In an alternative embodiment shown in FIG. 5a, the end 162a
of a screw 158a of an electrically driven motor is directly
connected to the end 32 of a pin 50. In such an embodiment, the
screw 158a and associated nut 154a act as an actuating mechanism.
As shown, a portion of the length of the screw 158a is threaded
with screw threads 156a which are screwably engaged within nut
component 154a. As schematically shown, nut component 154a is
mounted against axial movement (along axis X) on or to bearing 152a
which is in turn mounted against axial movement on or to motor
housing 64 which is in turn mounted against axial movement to
manifold 172a. As schematically shown, nut 154a is mounted on or to
the inner rotatable race of bearing 152a and is drivably rotated by
electrical power input to coils 174a around axis X. As nut 154a is
controllably rotated, screw 158a is controllably driven and travels
along axis X and pin 50 is simultaneously driven and travels
axially together with screw 158a. As shown, pin 50 is slidably
mounted in a complementary aperture in manifold 172a and a bushing
150a which seals against leakage of molten plastic. The pin 50
extends within melt channel 20 and is movable along its axis X
without rotation. By virtue of the direct coaxial connection
between screw 158a and pin 50, and the rigid mounting of nut 154a
against axial movement to housing 64 and the rigid mounting against
axial movement of housing 64 to manifold 172a via mounts 170a,
axial force to which the pin 50 is subject is transmitted axially
to the rotor of the motor 64. To provide for absorption of such
axial forces and to relieve the rotor of such load, the nut 154a is
mounted in, on or to bearing 152a which is rigidly mounted to the
housing of motor 64. Bearing 152a thus absorbs axial forces to
which the screw 158a is subject. As described above a controller
such as controller 176a, FIG. 5a which receives signals
representative of the output of a position sensor 178a is provided
having a program or instructions for executing an algorithm which
controls the input of electrical power to servomotor coils
174a.
[0195] FIGS. 6a-8a show another embodiment of the present invention
in which the shaft 60 of an electrically driven motor 64 is
drivably interconnected to a slidably mounted pin 50 through a
bevel gear engagement between the head 190 of a screw 72 and the
head 191a of an extension member 61 of the motor shaft 60. As can
be readily imagined, the screw component could alternatively have
threads along its length (in place of the beveled head 190a) which
mesh with a worm at the end of extension 61 (in place of the
beveled member 191a). As shown, the axis Y of the shaft 60 is
perpendicular to the axis X of the pin 50 and the actuating screw
mechanism 72 such that axial forces which may occur along axis X
are not transmitted along axis Y to the shaft 60.
[0196] In the FIGS. 6a-8a embodiment, the pin 50 has a nut 195
integrally forming the end of the pin 50 which is drivably
interconnected to, i.e. screwably engaged with, the actuating screw
72. The pin 50 is slidably mounted in a complementary aperture 90
within manifold 75 for movement along its axis X within melt flow
channel 20. The actuating screw 72 is mounted via disc 180a to
housing 58 which is, in turn, fixedly mounted to manifold 75 such
that screw 72 is drivably rotatable around axis X and axially
stationary along axis X. Screw 72 is drivably rotatable around axis
X via the screwable engagement between bevel gears 190a, 191a.
Shaft extension member 61 is coaxially connected to the motor shaft
60 (via rigid connection between connecting disc 210a and a
complementary connecting member attached to shaft 60 which is not
shown) such that as the shaft 60 is rotatably driven around axis Y
the extension member 61 and its associated bevel gear 191 are
simultaneously rotatably driven around axis Y. As can be readily
imagined, as screw 72 is rotatably driven around axis X via the
meshed bevel gears 190a, 191a, pin 50 is translationally driven
along axis X via the screwable engagement between nut end 195a and
screw 72. Thus the screw 72 acts as an actuating member to and
through which axial forces are transmitted to and from pin 50. As
described with reference to the previous embodiments, the
electrically driven motor 64 may be interconnected to a controller
which receives data/signals representative of melt flow or machine
component conditions and has a predetermined algorithm for
directing the drive of the motor according to the received
data/signals and the predetermined algorithm, program or
protocol.
* * * * *