Patent Publication Number: US-11396118-B2

Title: Actuator for controlling multiple injection molding valve pins

Description:
FIELD OF THE DISCLOSURE 
     This disclosure relates to injection molding apparatuses and more particularly to valve gate assemblies having actuators that simultaneously control flow of liquid resin through two or more injection nozzles. 
     BACKGROUND OF THE DISCLOSURE 
     Injection molding apparatus having actuators that control flow of liquid resin through two or more injection nozzles reduce the number of actuators needed to control flow of resin into multiple cavities defined in a mold or into multiple mold inlets to a single cavity, thus allowing closer nozzle centers while reducing both capital and operating expenses. Fastening means are provided to connect each valve pin to a valve pin carrier that is coupled to a cylinder rod of the actuator. Maintenance has required disassembly of each of the individual connections between the valve pin carrier and the valve pins, which are usually seized or frozen in place by solidified resin. Conventional disassembly involves prolonged service and maintenance time, and reduced production time. It is an object of this disclosure to provide a valve gate assembly that reduces service and maintenance time and increases production time. 
     SUMMARY OF THE INVENTION 
     This disclosure is directed to a valve gate assembly and actuator assembly that provides a quick disconnect and quick assembly arrangement that allows rapid and easy removal of an actuator assembly from multiple valve pins, and rapid and easy assembly of the actuator assembly onto multiple valve pins, thereby reducing the time needed to service the valve gate assembly or molding apparatus to which it is associated and increasing available production time. 
     The valve gate assembly includes a manifold defining multiple channels for delivering resin to multiple injection nozzles, a plurality of nozzles associated with a corresponding cavity or multiple cavities, a plurality of valve pins that move linearly within an axial bore in an associated nozzle to control flow of resin through the gate of the nozzle, one or several actuators having a linearly movable rod, a valve pin plate that is coupled to the rod and includes a valve pin coupler associated with each of the plurality of valve pins. 
     In certain embodiments, the valve pin coupler includes a valve pin head receiving section and a valve pin head retaining section. The valve pin head retaining sections hold the pins such that the pins move with liner movement of the valve pin plate and the rod of the actuator, and the valve pin receiving section allows insertion and extraction of the valve pin head. The plurality of valve pin couplers are oriented with respect to one another such that linear movement of the plate with respect to the valve pins causes all pins to move simultaneously between the associated retaining sections and receiving sections. A lock, such as a set screw, can hold the valve pin plate relative to the valve pins and actuator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an injection molding apparatus incorporating the valve gate assembly and actuator assembly of this disclosure. 
         FIG. 2  is a perspective view of the valve gate assembly shown in  FIG. 1 . 
         FIG. 3  is a perspective view of the actuator assembly shown in  FIGS. 1 and 2 , with portions broken away to show interior details. 
         FIGS. 4-7  are cross-sectional views of the actuator assembly of  FIG. 3  at various stages during disassembly thereof. 
         FIG. 8  is a top view of the valve pin plate from the actuator assembly of  FIG. 3 . 
         FIG. 9  is an enlarged top view of the pin retaining pocket defined in the valve pin plate of  FIG. 8 . 
         FIG. 10  is a perspective view of an alternative embodiment in which the actuator can be disengaged from a plurality of valve pins by a rotational movement. 
         FIGS. 11A-11D  are prospective views of an alternative valve plate configuration for facilitating removal of actuator assemblies from a hot runner system without removing valve pins from the manifold. 
     
    
    
     DETAILED DESCRIPTION 
     A hot runner assembly  10  (shown in cross-section in  FIG. 1 ) for an injection molding apparatus includes a heatable manifold  12  having a plurality of passageways that define a hot runner system that facilitates flow of a liquid resin (typically a thermoplastic polymeric composition) from an inlet channel  16  defined in sprue busing  17  to a plurality of nozzles  20 . The illustrated gate assembly includes a two-piece manifold  12 , including an upper manifold section  12 A and a lower manifold section  12 B. Locator pins  13  can be employed to ensure proper alignment of section  12 A with section  12 B. Manifold  12  is an example of a two-section manifold. However, the novel concepts of this disclosure can be used with manifolds having a single section or any number of sections. 
     Each nozzle  20  has a cylindrical shape and includes a cylindrical bore  26  extending along the cylindrical (or longitudinal) axis of the nozzle. An end of the cylindrical bore defines a gate  27 . Centered within the cylindrical bore  26  and extending from an actuator assembly  30  mounted on manifold  12  and generally through the cylindrical bore is a valve pin  28 . Valve pin  28  also has a generally cylindrical shape (circular transverse cross-section), with a diameter that is less than the diameter of the cylindrical bore  26 , and is generally centered within the bore  26  to define an annular volume  32  between the wall of bore  26  and the outer surfaces of valve pin  28 . Valve pin  28  is linearly movable along the longitudinal axis of nozzle  20  between a first position (shown on the left side of  FIG. 1 ) in which a lower end of the valve pin is seated in gate  27  to prevent flow from the nozzle into a mold cavity  34  defined by mold plate  36 , and a second position (shown on the right side of  FIG. 1 ) in which the lower end of valve pin  28  is spaced away from the gate. Upper end  38  of nozzle  20  can be provided with external threads that engage internal threads of a nozzle receiving bore of manifold  12  to facilitate disassembly of assembly  10  for maintenance. 
     The illustrated assembly  10  employs hot runner technology in which the channels and other conduits used for conveying liquid resin from an injection molding machine to cavities  34  are continuously maintained at an elevated temperature during normal operation by sprue heater  40 , manifold heater  42  and nozzle heater  44 . Heaters  40 ,  42  and  44  can be electrical resistance heaters. 
     Assembly  10  includes various support/alignment structures  46 ,  48 ,  50 ,  52  to facilitate proper and stable alignment and spacing of the assembly  10  with intermediate plate  54  and top plate  56 . 
     As can be seen by reference to  FIG. 2 , assembly  10  includes a plurality of nozzles  20  associated with each of actuator assemblies  30 . In the illustrated embodiment, flow of resin through three nozzles is regulated by each of two actuator assemblies  30 . However, this example is illustrative, and any number of nozzles can be associated with a single actuator assembly (e.g., 2, 3 or 4 nozzles can be controlled by a single actuator assembly). 
     An actuator assembly  30  and valve pins associated with nozzles  20  are shown in  FIG. 3 . Assembly  30  includes a cylinder actuator  60  (e.g., hydraulic, electric or pneumatic actuator) which can, for example, be a single acting actuator in which the working fluid acts on only one side of the piston  62  and a mechanical load, such as a spring or compressed air, acts on the other side to effect controlled linear movement of a drive rod  64  attached to piston  62 . Alternatively, a double acting actuator may be used in which the working fluid acts on both sides of the piston to control linear movement of valve pin plate  66  and rod  64 . 
     As shown in  FIG. 3 , actuator assembly  30  includes a piston housing  63  in which piston  62  is housed. Housing  63  is supported by a valve pin plate housing  65  in which valve pin plate  66  is disposed. A circumferential ledge or shoulder  67  extends radially inwardly from the upper edge of valve pin plate housing  65  with a vertical circumferential wall or collar  69  extending upwardly from a radially inward edge of shoulder  67 . Piston housing  63  is releasably supported on valve pin plate housing  65  with the lower edge of housing  63  supported on shoulder  67  and the lower end of the radially inwardly facing surface of housing  63  abutting the radially outwardly facing surface of collar  69 . Housing  63  is releasably secured to housing  65  by a plurality of screws  71  having a narrow or pointed end extending into a circumferential groove  11  on the outwardly facing surface of collar  69 . Screws  71  extend through openings  73  of piston housing  63 . 
     Piston  62  is retained and reciprocates within a chamber  75  defined by housing  63  and cap  77 , which is secured to housing  63  by snap ring  79 . A pin seal retaining disc  90  is retained on the manifold  12  with bolts. Housing  65  is secured to the manifold by bolts  83 . The pin seal retaining disc  90 , along with pin seals  88  and valve pin  28  also provide a seal against flow of molten resin upwardly from the manifold. 
     A valve pin plate  66  is connected to rod  64  and moves linearly with rod  64  as dictated by control of actuator  60 . Valve pin plate  66  is provided with a plurality of pockets  70  ( FIGS. 8 and 9 ) for releasably receiving and retaining valve pins  28 . Pockets  70  are at least partially lipped, the lips of each pocket being Configured to engage an underside of a head  72  ( FIG. 4 ) of valve pin  28 . Each pocket  70  has a pin head receiving section  74  ( FIGS. 8 and 9 ) that is configured to allow the head  72  to be inserted into the pocket, and a pin head retention section  76  that is narrower than the pin head and has ledges or lips  78  that are spaced apart to define a gap that is smaller than a diameter of the valve pin head  72  and at least equal to, or slightly larger than a diameter of the stem portion  80  of valve pin  28 , such that when the pin head  72  is located in the pin head retention section  76  of pocket  70 , valve pin  28  is held in pocket  70  and restricted from moving except linearly with valve pin plate  66 . The pin head insertion section  76  is configured (shaped and sized) such that when pin head  72  is located in the pin head retention section, valve pin plate  66  can be removed (lifted away) from the valve pins  28 . 
       FIG. 6  shows actuator  30  moved linearly with respect to the valve pins  28  to a position in which the pin heads  72  can pass through the pin head receiving sections  72 , to allow separation into components  99  as shown in  FIG. 7 . 
     Regardless of the number of pockets  70  for pins  28 , the pockets are oriented so that plate  66  can be either moved linearly or rotated (as shown in  FIG. 10 ) to simultaneously position all pins  28  in the pin head retention sections  76  to facilitate simultaneous control of flow through each associated nozzle  20 , or moved in the opposite direction to simultaneously position all pins  28  in the pin head insertion section  74  to facilitate separation of the actuator assembly  30  from the pins  28 . To allow separation of the actuator assembly from the pins using a linear motion, the straight portions of the pockets are arranged in parallel. To allow separation using a rotational motion, the lipped narrow part of the pockets can be arranged along a circular path in the plane of the valve plate. A lock  91  is used for holding the position of plate  66  relative to pins  28  such that pins  28  are held in the pin head retention section  76 . Illustrated lock  91  is a socket head screw received in a threaded bore extending from a lateral edge of plate  66 ′ to a surface of rod  64 ′. An opening  82  can be provided in a wall of actuator assembly housing  84  to provide access to the head of the set screw. Other mechanical locks (such as a spring loaded pin or latch mechanism) may be used as an alternative to a set screw. 
     In certain alternative embodiments, pockets  70  can be replaced with slots having a shape similar to pocket  70  ( FIG. 9 ), including a pin receiving section through which pin head  72  can pass and a narrower pin retention section that prevents pin head  72  from passing therethrough, with the underside of pin head  72  engaging an upper surface of plate  66 . 
     In certain embodiments, plate  66  can be provided with an aperture  86  ( FIG. 8 ) that facilitates removal of plate  66  from rod  64  when lock  81  is disengaged (e.g., unsecured) from rod  64 . Aperture  86  includes a larger diameter section through which a flanged nut can be passed and a narrow section through which the flange on the nut cannot be passed. 
       FIGS. 4-7  illustrates removal of actuator assembly  30  from pins  28 . In the fully assembled state ( FIGS. 1 and 4 ), pins  28  are guided by pin seals  88  held in pin seal retaining disc  90  secured to manifold  12 , with pin heads  72  retained in the lipped portions of pockets  70 . Simultaneous removal of actuator assembly  30  from all associated valve pins  28  is achieved by releasing lock  81  (e.g., unscrewing a screw) as shown in  FIG. 5 , moving the actuator assembly linearly (or rotatably) from an orientation wherein the pin heads  72  are positioned in the retentions section  76  to an orientation in which the pin heads  72  are positioned in the insertion/extraction section  74  of pockets  70  (as shown in  FIG. 6 ), and separating the actuator assembly from the pins (as shown in  FIG. 7 ). Installation is achieved by reversing the removal steps. The arrangement greatly simplifies decoupling of an actuator assembly from a plurality of valve pins. Another advantage is that because the valve pins remain with the manifold or hot runner assembly and are instead separated from the actuator assembly, the valve pins do not need to have their positions adjusted each time the system is serviced, thereby further reducing labor and production interruptions. 
     In the alternative embodiment shown in  FIG. 10 , which allows removal of pin heads  72  from pockets  70  by rotation (indicated by arrow  2 ) of valve pin plate  66 ′, a U-shaped retaining clip  85  securable to plate  66 ′ with bolt  87  secures plate  66 ′ to piston rod  64 ′. A screw  91  extends radially through the valve pin plate into the narrower portions of the pockets to block rotation of plate  66 ′ relative to the pins and pin seal retaining disc  90  during normal operation of hot runner assembly  10 . The actuator assembly is removed, while leaving pins  28  in the manifold, by first removing or loosening screw  91  (indicated by arrow  1  in  FIG. 10 ), then rotating the actuator assembly in the direction indicated by arrow  2  in  FIG. 10 , and finally lifting the actuator as indicated by arrow  3  in  FIG. 10 . 
     As shown in  FIG. 5 , a screw  81  extends through a threaded bore from a side of plate  66  to piston rod  64 . When the radially inward end of screw  81  is engaged with rod  64 , pin heads  72  of pins  28  are locked in place within the pin head retention sections  76  of pockets  70  for normal operation of hot runner assembly  10 . For servicing the actuators, screw  81  is rotated (e.g., counter-clockwise) to draw the inwardly facing end of screw  81  away from rod  64 . A screw access opening  82  through housing  65  can be configured so that when the head of screw  81  engages the inner surface of housing  65  adjacent opening  82 , further rotation causes disc  66  to move away from the head of screw  81  causing the pin heads to move toward the pin head insertion (and removal) sections  74  of pockets  70  to allow removal of the actuator assembly. 
       FIGS. 11A-11D  shows an alternative valve plate for facilitating removal of an actuator assembly  30  without removing valve pins  28 . The valve pin plate  166  includes a plurality of valve plate segments  166 A,  166 B,  166 C, which are bolted together, such as with bolts  97 , wherein the segments have interfacing surfaces that together define a pin head retention pocket  170 . In the illustrated segmented valve pin plate, three segments define three interfaces, with each interface configured to define a single pin head retention pocket. In general, it is preferred that each segment has two surfaces that interface with another segment to define a pin head retention pocket. For example, four segments could be used to define four pin head retention pockets at each of four interfaces. However, other arrangements are possible including a single interface defining two or more pockets, or an interface that does not define a pocket. Access openings  111  to bolts  97  are provided to allow loosening of the space between the segments to provide the needed clearance to remove the actuator assembly without removing pins  28 . 
       FIG. 11A  shows the actuator assembly  30  and segmented valve pin plate  166  in the fully assembled state for normal operation. Removal of the actuator for servicing is achieved by first loosening bolts  97  as indicated by arrows in  FIG. 11B . Next, the actuator assembly  30  is rotated slightly causing the interfacing surfaces of the segments to separate as shown in  FIG. 11C , allowing the actuator assembly  30  to be lifted from the manifold and valve pins  28 . 
     In certain embodiments, piston rod  89  can be provided with a bore at its lower end adjacent the manifold to reduce conductive heat transfer from the manifold to the actuator via rod  89 . 
     Because pins  28  remain with the manifold during removal of actuator assemblies  30  in accordance with this disclosure, pin positioning does not need to be adjusted to properly align the tip of the pins with the nozzle gate each time the actuators are removed for servicing, further reducing labor and periods of non-production. The upper end of piston rod  64  is provided with a hexagonal recess  93  (or other driver engagement feature) to facilitate pin position adjustment with a driver tool. 
     The above description is intended to be illustrative, not restrictive. The scope of the invention should be determined with reference to the appended claims along with the full scope of equivalents. It is anticipated and intended that future developments will occur in the art, and that the disclosed devices, kits and methods will be incorporated into such future embodiments. Thus, the invention is capable of modification and variation and is limited only by the following claims.