WO2012151269A1

WO2012151269A1 - Injection molding flow control apparatus and method

Info

Publication number: WO2012151269A1
Application number: PCT/US2012/036106
Authority: WO
Inventors: Vito Galati; Christopher W. Lee
Original assignee: Synventive Molding Solutions, Inc.
Priority date: 2011-05-02
Filing date: 2012-05-02
Publication date: 2012-11-08

Abstract

Apparatus for controlling the rate of flow of a pressurized fluid material injected from an injection molding machine to and through a gate (182) to a mold cavity (192) comprising: a fluid delivery channel (19), an electric actuator (10) interconnected to a valve pin (50) in an arrangement wherein the valve pin comprises a shaft (52) extending into the fluid delivery channel (19), the shaft (52) having a bulbous portion (112) disposed downstream of the shaft mounting aperture (54), the bulbous portion (112) having a maximum cross radial section that is greater than the cross radial section of all portions of the shaft (112) in contact with the pressurized fluid material upstream of the bulbous portion (112), the bulbous portion (112) forming an upstream facing surface against which the pressurized fluid material acts to exert a downstream directed force on the channel shaft.

Description

INJECTION MOLDING FLOW CONTROL APPARATUS AND METHOD

RELATED APPLICATIONS

[01] This application claims the benefit of priority to U.S. Provisional Application Serial No. 61/481 ,347 filed May 2, 201 1.

[02] The disclosures of all of the following are incorporated by reference in their entirety as if fully set forth herein: U.S. Patent No. 5,894,025, U.S. Patent No. 6,062,840, U.S. Patent No. 6,294,122, U.S. Patent No. 6,309,208, U.S. Patent No. 6,287,107, U.S. Patent No. 6,343,921 , U.S. Patent No. 6,343,922, U.S. Patent No. 6,254,377, U.S. Patent No. 6,261 ,075, U.S. Patent No. 6,361 ,300, U.S. Patent No. 6,419,870, U.S. Patent No. 6,464,909, U.S. Patent No. 6,599,116, U.S. Patent No. 6,824,379, U.S. Patent No. 7,234,929, U.S. Patent No. 7,419,625, U.S. Patent No. 7,569,169, U.S. Patent Application Serial No. 10/214,1 18, filed August 8, 2002, U.S. Patent No. 7,029,268, U.S. Patent No. 7,270,537, U.S. Patent No. 7,597,828, U.S. Patent Application Serial No. 09/699,856 filed October 30, 2000 (7056), U.S.

Application Serial No. 09/503,832 filed February, 15, 2000, U.S. Application Serial No. 09/656,846 filed September 7, 2000, U.S. Application Serial No. 10/006,504 filed December 3, 2001 and U.S. Application Serial No. 10/101 ,278 filed March, 19, 2002, U.S. application serial no. 13/235,892 filed September 19, 201 1 (7097), International Application PCT/US1 1/62099 filed November 23, 2011 (7100WO0) and International Application PCT/US1 1/62096 filed November 23, 2011 (7100WO1 ).

BACKGROUND OF THE INVENTION

[03] Injection molding systems have been developed having flow control mechanisms that control the movement of a valve pin over the course of an injection cycle to cause the pin to move either upstream or downstream over the course of injection cycle in order to raise or lower the rate of flow of fluid material to

correspond to a predetermined profile of fluid flow rates for the injection cycle. A sensor can be used to sense a condition of the fluid material or of the apparatus such as fluid pressure, fluid temperature, pin position and send a signal indicative of the sensed condition to a program contained in a controller that uses the signal as a variable input to control movement of the valve pin in accordance with the

predetermined profile.

[04] Use of an electric or electrical power driven actuator can be

advantageous when employing an electronic controller such as a computer or microprocessor to control movement of the actuator in addition to elimination of the need for oil, gas or pumps to drive the actuator. Electric actuators suffer for use in injection molding systems due to factors such as high cost, insufficient power, lack of durability and increased size and space of the actuator in a system that requires compactness.

SUMMARY OF THE INVENTION

[05] In accordance with the invention there is provided an apparatus for controlling the rate of flow of a pressurized fluid material injected from an injection molding machine to and through a gate to a mold cavity, the apparatus comprising: a fluid delivery channel that receives the pressurized fluid material and delivers the pressurized fluid material to a gate to the mold cavity;

an electric actuator interconnected to a valve pin in an arrangement wherein the valve pin comprises a shaft extending into the fluid delivery channel, the shaft having an axis and a distal end, an upstream portion of the shaft being slidably mounted in a shaft mounting aperture for slidable upstream-downstream movement therein;

the electric actuator being adapted to drive the shaft along a reciprocal upstream-downstream path within the fluid delivery channel at least between positions where the distal end of the shaft closes and opens the gate;

the shaft having a bulbous portion disposed downstream of the shaft mounting aperture, the bulbous portion having a maximum cross radial section that is greater than the cross radial section of all portions of the shaft in contact with the pressurized fluid material upstream of the bulbous portion, the bulbous portion forming an upstream facing surface against which the pressurized fluid material acts to exert a downstream directed force on the channel shaft. [06] The downstream directed force exerted on the upstream facing surface works in aid of drive force applied by the electric actuator when driving the shaft in a downstream direction.

[07] The electric actuator is preferably adapted to controllably adjust the distal tip end of the channel shaft to a multiplicity of positions relative to the gate, each position resulting in a different rate of flow of fluid material through the gate.

[08] The maximum cross radial section of the bulbous portion is preferably greater than or equal to the maximum cross radial section of all portions of the shaft in contact with the pressurized fluid material downstream of the bulbous portion.

[09] The upstream portion of the shaft mounted in the shaft mounting aperture typically has a radial cross section less than the maximum radial cross section of the bulbous portion of the shaft.

[10] The distal end of the shaft can have a tapered configuration and the gate can have a tapered surface complementary to the tapered configuration of the distal end of the shaft such that the distal end of the shaft is matable with the gate surface so as to close the gate and prevent flow of fluid material through the gate, the electrically powered actuator driving the shaft reciprocally between gate open and a gate closed position where the distal end of the shaft mates with the gate surface.

[11] The actuator can be interconnected to a controller that receives a signal from a sensor indicative of a sensed condition of the fluid material or the apparatus, the controller generating instructions based on a value corresponding to the received signal and controlling the actuator to drive the shaft to axial positions according to the instructions.

[12] The sensed condition can include a position of a mechanical member including a position of the shaft, a pressure of the fluid material and a temperature of the fluid material.

[13] The actuator can be interconnected to a controller that controllably adjusts the position of the shaft such that the distal end of the shaft varies the flow of fluid material through the gate during an injection cycle according to a predetermined algorithm. [14] In another aspect of the invention there is provided an apparatus for controlling the rate of flow of a pressurized fluid material injected from an injection molding machine to and through a gate to a mold cavity, the apparatus comprising: a fluid delivery channel that receives the pressurized fluid material and delivers the pressurized fluid material to a gate to the mold cavity;

the shaft having a bulbous portion disposed downstream of the shaft mounting aperture, the bulbous portion forming a radially widened, upstream facing surface along the axis of the shaft, the pressurized fluid material exerting a downstream directed force on the upstream facing surface that is greater than any upstream directed force exerted by the fluid material on all portions of the shaft in contact with the pressurized fluid material upstream of the bulbous portion.

[15] In such an apparatus the downstream directed force exerted on the upstream facing surface works in aid of drive force applied by the electric actuator when driving the shaft in a downstream direction.

[16] In another aspect of the invention there is provided, in an injection molding apparatus comprising a fluid injection machine that injects a pressurized fluid material to fluid delivery channel that delivers the fluid material to a gate to a mold cavity and an actuator interconnected to a valve pin comprising a shaft having an axis and a distal tip end,

a method for performing an injection molding cycle, the method comprising: selecting the actuator to comprise an electric motor and adapting the electric motor and the valve pin to enable the electric motor to drive the valve pin along a reciprocal upstream-downstream path within the fluid delivery channel between at least a gate closed and a gate open position,

forming the shaft with a bulbous portion along its axis having a selected maximum radial cross-section,

forming the shaft such that all portions of the shaft disposed upstream of the bulbous portion that are in contact with the fluid material have a radial cross-section that is less than the maximum radial cross-section of the bulbous portion, and,

powering or driving the actuator with electrical power or energy to drive the shaft axially upstream and downstream at least between gate open and gate closed positions during the course of the injection cycle.

[17] Such a method typically further comprises controllably driving the actuator to control the position of the distal tip end of the shaft relative to the gate such that the rate of flow of fluid material through the gate varies over the course of an injection cycle according to a predetermined program.

[18] Such a method can further comprise controllably driving the actuator to control the rate of movement of the valve pin from a gate closed position to a gate open position according to a predetermined program over the course of an injection cycle.

[19] In another aspect of the invention there is provided an apparatus for controlling drive of a valve pin in an injection molding system, the apparatus comprising:

an actuator comprising a drive shaft driven by an electrically powered drive mechanism;

a valve pin comprising a shaft having an axis and a distal tip end, the shaft being mounted in a mounting aperture having an exit to a fluid delivery channel into which pressurized fluid material is injected, the fluid delivery channel communicating at a downstream end with a gate to a mold cavity;

the valve pin being interconnected to the drive shaft of the electrically powered actuator in an arrangement such that the shaft of the valve pin is drivable along its axis in a reciprocal upstream-downstream manner within the fluid delivery channel between at least a downstream position where the distal tip end of the shaft closes the gate and an upstream position where the gate is fully open to maximum flow of fluid material through the gate;

the shaft having bulbous portion disposed downstream of the exit of the mounting aperture extending along a selected axial length of the shaft, the bulbous portion having a maximum radial cross section along its selected axial length that is greater than all radial cross sections taken along the entire axial length of the shaft that is upstream of the bulbous portion.

[20] In such an apparatus the radial cross section of a surface that is most distally disposed on the distal tip end of the shaft is greater than the radial cross section of all radial sections taken along the entire length of the shaft that is upstream of the bulbous portion.

Brief Description of the Drawings

[21] 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:

[22] Fig. 1 is a schematic cross-sectional view of a system incorporating one embodiment of the invention showing a valve pin having a cylindrical shaft with an upstream cross-sectional diameter of about 3-5 mm and downstream bulbous member 100 having a maximum cylindrical section with a cross-sectional diameter of about 6-9 mm and a conical configuration at its distal end;

[23] Fig. 2 is an enlarged sectional view of the distal end of a valve pin and shaft disposed within the fluid delivery channel of a nozzle mounted between a heated manifold and a mold, the shaft of the nozzle having a bulbous member disposed at its downstream end the bulbous member being cylindrical in

configuration at its downstream end;

[24] Fig. 3 is an enlarged sectional view of a system where the valve pin and shaft are mounted at their upstream proximal end in a mounting aperture of a heated manifold, the pin having a bulbous portion that extends over an extended portion of the axial length of the shaft, the bulbous portion having a distal downstream and tip end configuration that is cylindrical; [25] Fig. 4A is a cross sectional view of the distal end of a shaft of a valve pin having a bulbous member with a downstream conical configuration similar to Fig. 1 disposed at the distal end of the shaft, the shaft being disposed in the fluid delivery channel of a nozzle, the shaft being in a gate open position;

[26] Fig. 4B is a cross sectional view of the Fig. 4A device showing the shaft in a gate closed position;

[27] Fig. 5 is a perspective view of the distal end of valve pin and shaft showing a bulbous portion having a fluted configuration;

[28] Fig. 6 is a cross sectional view of the distal end of the Fig. 5 valve and shaft mounted and disposed for upstream-downstream movement within the fluid delivery channel of a nozzle that is mounted between a manifold and a mold;

[29] Fig. 7A is a cross sectional view of another embodiment of the invention showing a valve pin and flow channel having both an upstream flow restriction and a downstream flow restriction at the gate, the shaft being in a gate closed position;

[30] Fig. 7B is a view of the Fig. 7A embodiment showing the shaft in a gate open and upstream restriction open position;

[31] Fig. 7 C is a view of the Figs. 7A, 7B embodiment showing the shaft in a gate open and upstream restriction closed position.

DETAILED DESCRIPTION

[32] Fig. 1 shows an embodiment comprising an electric actuator 10 having motor that is driven by electricity or electrical energy E. The electric motor 0 drives a valve pin 50 in a reciprocal upstream-downstream UD manner along the axis A of the pin 50. The valve pin 50 has a shaft 52 that is mounted within and extends through a bushing 150 and mounting aperture 54 in a heated manifold or hotrunner 172. The shaft 52 extends into and through a fluid delivery channel 19 of the heated manifold or hotrunner 172. In the schematic embodiment shown, the downstream distal end of the fluid delivery channel 19 has a gate 182 that communicates with the cavity 192 of a mold 186. The gate 182 can be closed and opened by mating and unmating with a complementary surface 1 10 of a bulbous portion 1 12 of the shaft 52 of the pin 50. The shaft 52 is adapted to be disposed and driven reciprocally UD within the fluid delivery channel 19 that contains and routes pressurized fluid material injected into the channel 19 from an injection machine (not shown). The drive shaft of the motor or actuator 10 comprises a screw 158 which is directly connected at its downstream end 162 to the upstream proximal end 32 of the valve pin 50. The proximal end of a suitable valve pin can be connected to the drive shaft of an actuator in a variety of alternative ways. In the Fig. 1 embodiment, the screw 158 and an associated nut 154 that is screwably engaged with the threads 56 of the shaft 158 operate to cause the shaft to be driven along an upstream-downstream path UD in turn driving the interconnected valve pin 50. The nut 54 is driven by a magnet-coil assembly 174 that is attached to the circumferential surface of the nut 154. The assembly 174 is rotatably driven by electric power or energy E around axis A of the valve pin and drive shaft 158. As shown, a portion of the length of the screw 158 is threaded with screw threads 156 which are screwably engaged within nut component 154.

[33] As schematically shown, the nut component 154 is mounted against axial movement (along axis X) on or to bearing 152 which is in turn mounted against axial movement on or to motor housing 64 which is in turn mounted by mounts 170 against axial movement to manifold 172. As schematically shown, nut 154 is mounted on or to the inner rotatable race of bearing 152 and is drivably rotated by electrical power input E to coils 174 around axis A. As nut 154 is controllably rotated, screw 158 is controllably driven and travels UD along axis A together with pin 50 and shaft 52. As shown, pin 50 has a shaft 52 that is slidably mounted within a mounting aperture 54 that is complementary in size and contour to the size and contour of shaft 52 such that shaft 52 is readily slidably mounted within aperture 54 and substantially prevents upstream flow of fluid from channel 19 through aperture 54. The system is adapted such that shaft 52 extends through a bushing 50 and fluid distribution manifold 172 in a manner that effectively seals against significant leakage of pressurized molten fluid material or polymer from fluid delivery channel 19 upstream through mounting aperture 54 and the aperture within bushing 150. The mounting aperture 54 terminates at exit 56 and exits into the fluid delivery channel 19. The upstream portion UP of the shaft 52 as referred to herein is intended to refer to that portion of the shaft UP that is disposed within channel 19 and extends between the exit 56 of the mounting aperture 54 and the downstream bulbous portion 100 of the shaft 52.

[34] In the Fig. 1 embodiment, pin 50 extends into melt channel 19 and is interconnected to actuator 10 such that pin 50 and shaft 52 are movable along its axis A without rotation around axis A. By virtue of the direct coaxial connection between screw 158 and pin 50, and the rigid mounting of nut 154 against axial movement to housing 64 and the rigid mounting against axial movement of housing 64 to manifold 172 via mounts 170, axial force to which the pin 50 is subject is transmitted axially to the rotor or shaft 158 of the motor 10. To provide for absorption of such axial forces and to relieve the rotor of such load, the nut 154 is mounted in, on or to bearing 152 which is rigidly mounted to the housing of motor 10. Bearing 152 thus absorbs axial forces to which the screw 158 is subject.

[35] As shown, a controller 176 can be provided for receiving and

processing signals from a sensor 178 that senses a selected condition C of the fluid material, the injection machine, the hotrunner or manifold, the actuating system or the mold 186, 188 or mold cavity 192. The sensor 178 can comprise a variety of sensor mechanisms that sense a variety of conditions typically a condition of the fluid such as pressure or temperature or the position of a physical component of the apparatus. A typical sensor is a sensor that senses position such as pin or actuator position or a fluid material property sensor such as a pressure sensor or temperature sensor. A pin position or actuator position sensor can comprise any conventional position sensing mechanism such as an optical or mechanical detection system that detects the rotation of the actuator shaft or motor, an LVDT sensor system, a mechanical sliding rod sensor system with linear potentiometer, a limit switch assembly, a Hall effect sensor assembly and position sensors as described in U.S. Patent No. 7,044,728 and E.P Patent No. 2,047,961 the disclosures of which are incorporated herein by reference. The controller 176 typically includes a program for executing an algorithm which controls the input of electrical power to servomotor coils 174 to controllably position the distal end portion 1 10 of a bulbous portion 100 of the shaft 52 relative to a surface 180 of the gate 182 such that the flow of fluid material flowing through channel 19 and ultimately through the gate 182 is

controllably variable via the controller during the course of an injection cycle.

[36] The electric actuator 10 powered system of the present invention can also be used in a system in which the rate of upstream withdrawal of the pin 50 from a gate closed position to a gate open position is varied over predetermined amounts of time such that the pin 50 is withdrawn under power of the electric actuator 50 at a first slower rate of withdrawal for a first predetermined amount of time and then after the expiration of the first predetermined amount of time, the pin 50 is withdrawn at a second rate of withdrawal typically a maximum rate such that the pin is withdrawn all the way to its most fully upstream position at such maximum rate.

[37] In the FIG 1 embodiment, the injection molding system comprises a manifold 172, a top clamp plate system (not shown) and the electric or electrically powered actuator 0 mounted via mounts 170 on the manifold 172. In the Fig. 1 embodiment, the bulbous portion 100 of the shaft 52 is disposed at or near the distal end 110 of the shaft 52. The shaft 52 is disposed within the channel 19 such that the outside surface area of the shaft 52 is in contact with pressurized fluid material flowing through the channel 19. The bulbous portion 100 has an upstream facing surface 112 that is larger in radial cross section than the radial cross section of all portions of the shaft 52 that are upstream UP of the bulbous portion 100.

[38] The term radial cross section or radial section or cross radial section as used herein means the area taken along a radial cross section of the shaft 52 or other component or element being referred to at a particular point along the length of the axis A. Since the most typical embodiments of valve pins 50, shafts 52 and bulbous portions 100 are circular in radial cross-section, the term radial cross section or radial section can also mean the diameter or radius taken along a radial cross section of the shaft 52 or other component at a particular point along the axis A because size of radial cross sectional area is dependent on size of diameter or radius.

[39] More particularly, at a minimum, the bulbous portion 100 has a maximum radial cross section S2 that is larger than the maximum radial cross section S1 of the upstream portion of the shaft UP that is disposed within the channel 19 in contact with the fluid material. In the embodiment shown in Fig. 1 , the upstream portion UP of the shaft 52 that is disposed within the channel 19 is cylindrical with a single radial cross section S1 area or radial cross-sectional diameter of typically between about 3 and about 5 mm (in embodiments where the upstream portion UP is cylindrical), the upstream facing surface 112 of the

downstream bulbous portion 100 being conical (or partially conical) in configuration terminating at its downstream end in a shortened cylindrical section 114 having a single maximum radial cross section S2 or radial cross-sectional diameter along the length of its axis of between about 6 and about 9 mm. The downstream terminus of the shortened cylindrical section converts into a downstream facing conical section 110 having a downstream facing surface 120 and tip end surface 122 that can control the size of the gap 184 between the downstream surfaces 120, 122 and the surface 180 of the gate area. The rate of flow of fluid material through the gate 182 is thus controllably variable by controlling the size of the gap 184 by controlling the precise up or down UD axial position of the surface 120 relative to the gate surface 180. When the shaft 52 is driven to a fully downstream position the surface 120 mates with the gate surface 180, the gate 182 is closed and the fluid flow through gate 182 is stopped completely, the gate surface 180 and bulbous shaft portion surface 120 being configured to be complementary so that they can mate to prevent fluid from flowing between the two surfaces 120, 180 on driving of shaft 52 to its furthest downstream position.

[40] In conventional systems, the configuration of a valve pin shaft 52 typically does not include a bulbous portion 100 or an upstream facing surface such as surface 112 anywhere along its axial length. In such conventional systems the shaft 52 has a uniform radial cross-section and is cylindrical along the entire axial length of the shaft 52 disposed within the channel 19. In such conventional systems, a downstream facing surface such as the flat tip distal end surface 122 of the shaft 52 or its equivalent exists by necessity providing a surface against which the pressurized fluid material acts to exert an axially A oriented upstream force UF with no counteracting downstream force DF thus requiring a higher power, larger sized actuator to drive against the upstream force UF.

[41] In the Fig. 1 system, in addition to downstream facing conical surface 120, the shaft 52 also has a distal-most disposed tip end surface 122 that faces in a downstream direction. The downstream facing surfaces 120, 122 each provide a downstream facing contact surface having an axially oriented component against which pressurized fluid pushes within the channel 19 to exert an axially A oriented upstream force UF that acts against any axially A oriented downstream drive force applied by the actuator shaft 158 along the axis A when the motor 10 drives the shaft 158 in a downstream direction. To counteract the downstream facing surfaces 120, 122 and upstream force UF, the Fig. 1 system also includes an upstream facing surface 112 formed on the bulbous member 100. The surface 112 provides an upstream facing contact surface having an axially oriented component against which pressurized fluid within the channel 19 pushes to exert an axially A oriented downstream force DF on the shaft 52 via contact with the upstream facing surface 112. Such downstream force DF counteracts the upstream force UF and assists any axially A oriented downstream drive force exerted by drive shaft 158 on the shaft 52, the drive shaft 158 being driven by electric energy E via magnet-coil assembly 174. Thus the upstream facing surface 112 enables the actuator 10 to be downsized in power output capability and in physical size relative to a system that does not have an upstream facing surface 112 thus rendering an electric actuator system that incorporates an upstream facing surface 112 less costly and more space efficient. The provision of the upstream facing surface 112 further enables the size of the radial section surface area or diameter (or radius or area), such as diameter TD, Figs. 4A, 4B, 5, 6, to be increased or maximized which in turn enables the size of the gate 182 to be enlarged for purposes of increasing the volume of fluid flow through gate 182 without having to increase the size or power of the actuator 10.

[42] Fig. 2 and 3 show systems where an electric actuator 10 drives a valve pin 50 and shaft 52 that are disposed within the flow channel 19 of a nozzle 12 mounted within a receiving cavity 192 of a mold or mold plates 186, 188 and a spacer or retainer plate 190, the flow channel 19 of the nozzle 12 communicating between a hotrunner or manifold flow channel and a mold cavity 192. The shaft 52 has a bulbous portion 100 that is disposed generally at the distal downstream end of the shaft 52. The bulbous portion 100 has an upstream conical section having upstream facing surface 112 that extends between the downstream end of the cylindrical upstream portion UP and the cylindrical downstream portion of the bulbous portion.

[43] In the Fig. 2 embodiment, the downstream cylindrical portion of the bulbous member 100 has a relatively short axial length SL, its maximum diameter S2 (or radius or area) beginning at axial point or position MD. The axial length SL is shorter than the axial length of the portion UP of the shaft 52 that is upstream of the bulbous portion 100 and disposed within the channel 19. In the Fig. 3 embodiment, the downstream cylindrical portion of the bulbous member 100 has a relatively extended axial length EL, its maximum downstream diameter S2 (or radius or area) beginning at axial point or position MD. The axial length EL is longer than the axial length of the portion UP of the shaft 52 that is upstream of the bulbous portion 100 and disposed within the channel 19. Similar to the Fig. 1 embodiment, the Figs. 2 and 3 embodiments have an upstream facing surface 112 against which fluid material engages to exert a downstream axial force DF on the pin 50. The most distal tip end portion 124 of the shaft 52 in the Figs. 2, 3 embodiments is cylindrical with a diameter of S2 (or radius or area). The inside surface 180 of the gate 182 is complementary in size and contour to the distal portion 124 such that the outside surface of portion 124 of the shaft 52 mates with the inside surface 180 to close the gate 182 and stop fluid flow through the gate 182 when the surfaces 124, 180 are mated.

[44] The sole downstream facing surface in the Figs. 2 and 3 embodiments is the most distal tip end surface 122 against which fluid material acts to exert an upstream axial force UF. The maximum radial cross-section S2 of the bulbous portion 100, typically ranging from about 6 to about 9 mm in diameter, is greater than the maximum radial cross section S1 of the upstream portion UP, typically ranging from about 3 to about 5 mm in diameter. [45] Figs. 4A, 4B show an embodiment where the bulbous portion 100 is disposed generally at the distal end of the shaft 52. The bulbous portion 100 has an upstream facing surface 112 forming an upstream conical or partially conical member the downstream end of which forms into a shortened cylindrical section 1 14 having a maximum radial cross-section S2. The downstream end of the short conical section 114 forms into a downstream conical section having a downstream facing surface 20 similar to the Fig. 1 embodiment. The most distal tip end surface 122 of the shaft 52 has a diameter TD (or radius or area) that is less than the maximum diameter S2 (or radius or area) of the bulbous portion 100 but greater than the maximum diameter S1 (or radius or area) of the upstream portion UP of the shaft 52. The shape or configuration of the interior surface 180 of the gate 182 to the mold 186 and mold cavity 192 is complementary to the configuration or shape of the downstream facing surface 120 of the shaft such that the two surfaces 120, 180 can mate with each other as shown in Fig. 4B to close the gate 182 off to flow of fluid material when the shaft is driven fully downstream to its gate closed position as shown in Fig. 4B. As shown, the diameter TD (or radius or area) of the gate 182 is complementary to or the same as the diameter TD (or radius or area) of the most distal tip end surface 122 of the shaft 52. As in the Figs. 1-3 embodiments the upstream facing surface provides a downstream axial force DF on contact with the fluid material in the channel 19 and the downstream facing surfaces 120, 122 both provide upstream axial forces UF on contact with the fluid material.

[46] In another embodiment shown in Figs. 5, 6, a valve pin 50 is provided with contoured flutes or wings F disposed around the distal end of the shaft 52. The flutes F are evenly spaced around the axis A of the shaft. The bulbous portion 00 comprises the flutes F and adjacent conically contoured portions 132, 134 of the shaft 52. The flutes F have a maximum diameter of S2 (or radius or area) that is larger than the maximum diameter (or radius or area) of the upstream portion UP of the shaft 52. The flutes F include upstream facing surfaces 1 12 that act together with upstream facing surfaces 132 to provide a downstream axial force DF on contact with the fluid material. The flutes F also include downstream facing surfaces 120 which together with the distal most downstream facing surface 122 of the tip end provide an upstream axial force UF on contact with the fluid material. The diameter TD (or radius or area) of the tip end 122 is greater than the maximum radial cross- section or diameter S1(or radius or area) of the upstream UP portion of the shaft 52. As shown the cylindrical distal end portion 140 of the shaft has a relatively short axial length AL that is less than the axial length of the flutes F and the upper portion UP of the shaft 52. The interior surface 180 of the gate 182 is complementary in size and contour to the end portion 140 such that the surface 140 can mate with surface 180 and close off gate 182 to fluid flow on mating.

[47] The upstream proximal end of the pin 50 can be interconnected to the drive shaft 58 in alternative manners as described in the disclosures incorporated by reference above. Similarly, electric powered actuators 10 of varying structures and arrangements can be employed as described in the disclosures incorporated by reference.

[48] Figs. 7A-7C show another embodiment of the invention where the interior surface of the bore of the nozzle 12 flow channel 19 has an upstream section 14, 16 that is restricted in cross section relative to the other upstream and

downstream portions of the channel 19, the restricted section typically being formed as a shortened cylindrical channel 14 having a cylindrically shaped interior surface 16 having a cross-section S2 (diameter or radius or area) that is complementary to the maximum cross section MD, S2 (diameter or radius or area) of the downstream bulbous portion 100. The restriction section 14, 16 of the flow channel 19 is disposed along the axial length of the channel in a location relative to the location and axial length of the bulbous portion 100 such that when the tip end 122 of the shaft 52 closes the gate 182 as in Fig. 7A, the restriction section 14, 16 is fully open to flow of fluid material through the channel 19. The bulbous portion 100 and restriction section 14, 16 are further arranged and adapted such that the shaft 52 and pin 50 can be withdrawn in an upstream direction a certain distance as in Fig. 7B wherein both the gate 182 is open and the restriction section 14, 16 is open to fluid flow. On further withdrawal of the shaft 52 upstream from the position shown in Fig. 7B toward the position shown in Fig. 7C, the downstream flow of fluid through channel 19 and restriction 14, 16 can be reduced to less than the maximum flow depending on the precise position of upstream facing surface 112 relative to restriction surface 16, the closer surface 112 is to surface 16, the less or slower the flow of fluid through restriction 16 and gate 182 will be. On further withdrawal of shaft 52 upstream to the position shown in Fig. 7C, the outside surface 114 of the bulbous portion 100 mates with the complementary surface 16 and the flow of fluid material is stopped. The contoured upstream surface 112 and the upstream force UF created by the fluid against downstream facing surfaces 120, 122 assist the actuator 10 is effecting upstream withdrawal of the shaft. As in the other embodiments described herein, the upstream portion UP of the shaft 52 is smaller is radial cross-section S1 (diameter or radius or area) than the maximum radial cross- section S2, MD (diameter or radius or area) of the bulbous portion 100. And the Figs. 7A-7C embodiment has an upstream facing surface 112 which creates a downstream force DF that reduces the amount of downstream force, power or energy required to drive shaft 52 downstream relative to the amount of force required to drive a shaft that has no bulbous portion disposed in the fluid flow channel 19.

[49] Industrial Applicability

The disclosed apparatuses are particularly suitable for injection molding large parts having relatively large cavities and requiring injection of relatively large volumes of fluid material. The valve pin 50 and shaft 52 configurations provide upstream facing surfaces 112, 132 and the like that provide a downward axial force DF on the pin 50 that assists the downstream drive operation of an electric or electrically powered actuator 10 in such large part applications. The size of the gate 182 can be increased for purposes of increasing volume of flow of fluid material to the mold cavity 192 using an electrically powered actuator 10 that is relatively small in size.

Claims

1. An apparatus for controlling the rate of flow of a pressurized fluid material injected from an injection molding machine to and through a gate to a mold cavity, the apparatus comprising:

a fluid delivery channel that receives the pressurized fluid material and delivers the pressurized fluid material to a gate to the mold cavity;

the shaft having a bulbous portion disposed downstream of the shaft mounting aperture, the bulbous portion having a maximum cross radial section that is greater than the cross radial section of all portions of the shaft in contact with the pressurized fluid material upstream of the bulbous portion, the bulbous portion forming an upstream facing surface against which the pressurized fluid material acts to exert a downstream directed force on the channel shaft.

2. The apparatus of claim 1 wherein the downstream directed force exerted on the upstream facing surface works in aid of drive force applied by the electric actuator when driving the shaft in a downstream direction.

3. The apparatus of claim 1 wherein the electric actuator is adapted to adjust the distal tip end of the channel shaft to a multiplicity of positions relative to the gate, each position resulting in a different rate of flow of fluid material through the gate.

4. The apparatus of claim 1 wherein the maximum cross radial section of the bulbous portion is greater than or equal to the maximum cross radial section of all portions of the shaft in contact with the pressurized fluid material downstream of the bulbous portion.

5. The apparatus of claim 1 wherein the upstream portion of the shaft mounted in the shaft mounting aperture has a radial cross section less than the maximum radial cross section of the bulbous portion of the shaft.

6. The apparatus of claim 1 wherein the distal end of the shaft has a tapered configuration and the gate has a tapered surface complementary to the tapered configuration of the distal end of the shaft such that the distal end of the shaft is matable with the gate surface so as to close the gate and prevent flow of fluid material through the gate;

the electrically powered actuator driving the shaft reciprocally between gate open and a gate closed position where the distal end of the shaft mates with the gate surface.

7. The apparatus of claim 1 wherein the actuator is interconnected to a controller that receives a signal from a sensor indicative of a sensed condition of the fluid material or the apparatus, the controller generating instructions based on a value corresponding to the received signal and controlling the actuator to drive the shaft to axial positions according to the instructions.

8. The apparatus of claim 7 wherein the sensed condition includes position of a mechanical member including position of the shaft, pressure of the fluid material and temperature of the fluid material.

9. The apparatus of claim 1 wherein the actuator is interconnected to a controller that controllably adjusts the position of the shaft such that the distal end of the shaft varies the flow of fluid material through the gate during an injection cycle according to a predetermined algorithm.

10. An apparatus for controlling the rate of flow of a pressurized fluid material injected from an injection molding machine to and through a gate to a mold cavity, the apparatus comprising:

a fluid delivery channel that receives the pressurized fluid material and delivers the pressurized fluid material to a gate to the mold cavity; an electric actuator interconnected to a valve pin in an arrangement wherein the valve pin comprises a shaft extending into the fluid delivery channel, the shaft having an axis and a distal end, an upstream portion of the shaft being slidably mounted in a shaft mounting aperture for slidable upstream-downstream movement therein;

11. The apparatus of claim 1 wherein the downstream directed force exerted on the upstream facing surface works in aid of drive force applied by the electric actuator when driving the shaft in a downstream direction.

12. In an injection molding apparatus comprising a fluid injection machine that injects a pressurized fluid material to fluid delivery channel that delivers the fluid material to a gate to a mold cavity and an actuator interconnected to a valve pin comprising a shaft having an axis and a distal tip end,

forming the shaft such that all portions of the shaft disposed upstream of the bulbous portion that are in contact with the fluid material have a radial cross-section that is less than the maximum radial cross-section of the bulbous portion, and, powering or driving the actuator with electrical power or energy to drive the shaft axially upstream and downstream at least between gate open and gate closed positions during the course of the injection cycle.

13. The method of claim 12 further comprising controllably driving the actuator to control the position of the distal tip end of the shaft relative to the gate such that the rate of flow of fluid material through the gate varies over the course of an injection cycle according to a predetermined program.

14. The method of claim 12 further comprising controllably driving the actuator to control the rate of movement of the valve pin from a gate closed position to a gate open position according to a predetermined program over the course of an injection cycle.

15. Apparatus for controlling drive of a valve pin comprising:

16. The apparatus of claim 15 wherein the radial cross section of a surface that is most distally disposed on the distal tip end of the shaft is greater than the radial cross section of all radial cross sections taken along the entire length of the shaft that is upstream of the bulbous portion.