Abstract:
An injection molding apparatus includes a manifold having a manifold channel for receiving a melt stream of moldable material under pressure and delivering the melt stream to a nozzle channel of a nozzle. The manifold includes a manifold plug fit within a bore thereof and having a plug melt channel for fluidly connecting the manifold melt channel and the nozzle melt channel. The manifold plug further includes a valve/pressure disk portion that abuts with a back plate of the injection molding apparatus to maintain the spacing therebetween and to accommodate thermal expansion of the manifold relative to the back plate. In an injection molding application utilizing a valve-gated nozzle, the manifold plug may further include a valve pin receiving/guiding bore that functions as a valve pin bushing for a valve pin. A mold cavity communicates with the nozzle channel of the nozzle to receive melt through a mold gate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application claiming the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 60/619,684 filed Oct. 19, 2004. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an injection molding apparatus and, in particular, to a manifold plug for use in a manifold. 
     2. Related Art 
     Manifolds for injection molding systems often include manifold plugs for changing direction of the melt flowing through manifold melt channel, for example, turning the melt channel towards a hot runner nozzle. Manifold plugs are utilized because it is more cost effective to drill out a section of a manifold in which to insert the manifold plug than it is to drill a melt channel including turns directly into the manifold. 
     Injection molding systems using valve gating often include a valve pin bushing bridging the air gap between the manifold and the back plate in order to guide the valve pin and prevent leakage of melt from the manifold. A valve pin bushing is shown, for example, in U.S. Pat. No. 4,740,151 to Schmidt et al. The Schmidt et al. patent shows a separate manifold plug and a nozzle bolted to the manifold. Utilization of separate pieces to perform the functions of guiding the valve pin, changing direction of the manifold melt channel, and connecting the nozzle to the manifold requires very tight tolerances. Variations in expansion rates and movement during heating can cause such multiple parts to become misaligned, resulting in leakage. Further, having such multiple parts requires a larger inventory. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, an injection molding apparatus is provided having a manifold with a manifold channel for receiving a melt stream of moldable material under pressure and delivering the melt stream to a nozzle channel of a hot runner nozzle. The manifold includes a manifold plug fit within a bore thereof and having a manifold plug melt channel for fluidly connecting the manifold melt channel and the nozzle melt channel. The manifold plug further includes a pressure disk portion that abuts with a back plate of the injection molding apparatus to maintain the spacing therebetween and to accommodate thermal expansion of the manifold relative to the back plate. The present invention may be used with valve-gated or thermal gated hot runner nozzles. In an injection molding application utilizing a valve-gated nozzle, the manifold plug may further include a valve pin receiving/guiding bore that functions as a valve pin bushing for a valve pin. A mold cavity communicates with the nozzle channel of the hot runner nozzle to receive melt through a mold gate. 
     In one embodiment, the manifold plug is provided with a threaded portion receivable within a threaded recess of the hot runner nozzle such that the nozzle and manifold have a threaded connection. In another embodiment, a back end of the hot runner nozzle abuts with a downstream end of the manifold plug to allow for sliding therebetween during thermal expansion. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the present invention will now be described more fully with reference to the accompanying drawings in which like reference numerals indicate similar structure. 
         FIG. 1  is a side sectional view of a portion of an injection molding apparatus according to an embodiment of the present invention. 
         FIG. 2  is an isometric view of a manifold plug of  FIG. 1 . 
         FIG. 3  is an isometric view in section of a manifold plug according to another embodiment of the present invention. 
         FIG. 4  is a side sectional view of a portion of an injection molding apparatus according to another embodiment of the present invention. 
         FIG. 5  is a side sectional view of a portion of an injection molding apparatus according to another embodiment of the present invention. 
         FIG. 6  is a side sectional view of a portion of an injection molding apparatus according to still another embodiment of the present invention. 
         FIG. 7  is a side sectional view of a portion of an injection molding apparatus according to another embodiment of the present invention. 
         FIG. 8  is an enlarged view of portion A of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , an injection molding apparatus  10  is generally shown. Injection molding apparatus  10  includes a manifold  12  having a manifold melt channel  14 . A manifold plug  22  is received in a bore  24  that is provided in the manifold  12 . The manifold plug  22  includes a melt channel  26  that extends therethrough to redirect the melt flow between the manifold melt channel  14  and a manifold outlet  18 . Inlet  16  of manifold melt channel  14  receives melt from a machine nozzle (not shown) through a sprue bushing (not shown) and delivers the melt to a hot runner nozzle  20 , which is in fluid communication with manifold outlet  18 . 
     The nozzle  20  is received in an opening  28  in a mold plate  30 . Nozzle  20  includes a recess  36  that receives a downstream end  32  of the manifold plug  22 . The nozzle  20  is coupled to the downstream end  32  of the manifold plug  22  by a threaded connection  34 . Nozzle  20  is heated by a heating element (not shown) that is wound around the nozzle  20  and is received in grooves  38 , which are provided in an outer surface  40  of the nozzle  20 . The nozzle  20  further includes a thermocouple (not shown). 
     Although only a single hot runner nozzle  20  is shown in  FIG. 1 , it will be appreciated that a typical injection molding apparatus may include a plurality of manifold outlets such that each manifold outlet  18  delivers melt to a respective hot runner nozzle. 
     A nozzle tip  42  is received in a downstream end of nozzle  20 . Nozzle tip  42  is coupled to nozzle  20  by a transfer seal  44 . A nozzle melt channel  46  extends through nozzle  20  and nozzle tip  42 . Nozzle melt channel  46  is in communication with manifold outlet  18  and receives melt from manifold channel  14 . A mold cavity (not shown) receives melt from nozzle melt channel  46  through a mold gate  48 . Cooling channels (not shown) cool the mold cavity. Manifold  12  is maintained in position relative to mold plate  30  by a locating ring  50 . Spacers  52  and  54  are provided between manifold  12  and a back plate  56  and manifold  12  and mold plate  30 , respectively. Cooling channels  57  cool back plate  56 . 
     A cavity  58  is provided in back plate  56  for receiving an actuator (not shown) for a valve pin (not shown). The actuator may be any suitable type, such as pneumatic or hydraulic, for example. The valve pin selectively engages mold gate  48  to control melt flow into the mold cavity. 
     Referring also to  FIG. 2 , manifold plug  22  includes a valve/pressure disk portion  62  having an upper surface  64  that contacts a lower surface  66  of back plate  56 . In one embodiment, the valve disk is made as an integral part of the manifold plug, such that the manifold plug and valve disk are one piece. The valve disk  62  further includes a generally conical shaped body  68  that reduces in cross-sectional area between the upper surface  64  and a neck  70 . A valve pin receiving bore  72  extends through the manifold plug  22  and joins the melt channel  26  of the manifold plug  22 . The valve pin receiving bore  72  of the manifold plug  22  functions like a valve pin bushing for the valve pin. 
     Manifold plug  22  is press fit into the manifold bore  24 . A dowel  60  is received in an aperture  74 , which is provided in an outwardly extending flange  76  of the manifold plug  22 . The dowel  60  engages a recess  61  in manifold  12  to maintain the manifold plug  22  in a proper orientation in the bore  24  during the press fitting operation and subsequent operation in the injection molding apparatus  10 . 
     In operation, melt is injected from the machine nozzle through the sprue bushing, manifold channel  14  of manifold  12 , melt channel  26  of manifold plug  22 , nozzle melt channel  46  of nozzle  20 , and mold gate  48  and into the mold cavities. The melt in the mold cavities is then cooled and the molded parts are ejected from injection molding apparatus  10 . 
     Referring to  FIG. 3 , another embodiment of a manifold plug  22   a  is shown. In this embodiment, a recess  78  is cut into upper surface  64   a  of valve disk  62   a . The recess  78  increases the flexibility of the valve disk  62   a  in order to improve the deflection capability of the valve disk  62   a  during thermal expansion. Valve disk  62   a  further includes a pair of apertures  80 . The apertures  80  are included in order to provide a drain passage for melt in the event of leakage. 
       FIGS. 4 to 8  show further embodiments in which like reference numerals are used to identify like parts. 
     Referring to  FIG. 4 , another embodiment of an injection molding apparatus  10   b  is shown. This embodiment is similar to the embodiment of  FIG. 1 , however, a separate actuator  82  is provided on top of valve disk  62   b  of manifold plug  22   b . The actuator  82  includes a piston  84  that is slidable in a cylinder  86 . A valve pin  83  is coupled to a lower surface of a plate  88 . The valve pin  83  is selectively retractable by the actuator  82  to open and close mold gate  48   b . Seals  85 ,  87 , and  89  are disposed on each side between the piston  84  and the cylinder  86  to prevent leakage of fluid from the actuator  82 . As would be apparent to those skilled in the art, and piston/cylinder arrangement as shown in  FIG. 4  can be used in the other embodiments shown herein. 
     Another embodiment of an injection molding apparatus  10   c  is shown in  FIG. 5 . The injection molding apparatus  10   c  is thermally gated and therefore does not include either an actuator receiving cavity in a back plate  56   c  or a valve pin receiving bore in a manifold plug  22   c . Thermal gating is well known in the art and therefore will not be described here. 
     Injection molding apparatus  10   c  includes a manifold  12   c  having a manifold melt channel  14   c . Manifold plug  22   c  is received in a bore  24   c  that is provided in the manifold  12   c . Manifold plug  22   c  includes a pressure disk  62   c  positioned against back plate  56   c  for maintaining the spacing therebetween and for accommodating thermal expansion of manifold  12   c  relative to back plate  56   c . The manifold plug  22   c  includes a melt channel  26   c  that extends therethrough to redirect the melt flow between the manifold melt channel  14   c  and a manifold outlet  18   c . Inlet  16   c  of manifold melt channel  14   c  receives melt from a machine nozzle (not shown) through a sprue bushing (not shown) and delivers the melt to a hot runner nozzle  20   c , which is in fluid communication with manifold outlet  18   c.    
     The nozzle  20   c  is received in an opening  28   c  in a mold plate  30   c . The nozzle  20   c  is coupled to a downstream end  32   c  of the manifold plug  22   c  by a threaded connection  34   c . Nozzle  20   c  includes a recess  36   c  that receives the downstream end  32   c  of the manifold plug  22   c . Nozzle  20   c  is heated by a heating element (not shown) that is wound around the nozzle  20   c  and is received in grooves  38   c , which are provided in an outer surface  40   c  of the nozzle  20   c . The nozzle  20   c  further includes a thermocouple (not shown). 
     A nozzle tip  42   c  is received in a downstream end of nozzle  20   c . Nozzle tip  42   c  is coupled to nozzle  20   c  by a transfer seal  44   c . A nozzle melt channel  46   c  extends through nozzle  20   c  and nozzle tip  42   c . Nozzle melt channel  46   c  is in communication with manifold outlet  18   c  and receives melt from manifold channel  14   c . A mold cavity (not shown) receives melt from nozzle melt channel  46   c  through a mold gate  48   c . Cooling channels (not shown) cool the mold cavity. Manifold  12   c  is maintained in position relative to mold plate  30   c  by a locating ring  50   c . Spacers  52   c  and  54   c  are provided between manifold  12   c  and back plate  56   c  and manifold  12   c  and mold plate  30   c , respectively. Cooling channels  57   c  cool back plate  56   c.    
     Referring to  FIG. 6 , another embodiment of an injection molding apparatus  10   d  is shown. In this embodiment, a downstream end  32   d  of a manifold plug  22   d  is flush with a lower surface  13  of manifold  12   d  to allow nozzle  20   d  to slide relative to manifold plug  22   d  during thermal expansion. 
     Nozzle  20   d  includes a nozzle head  90  having a flange  92 . The flange  92  abuts a step  94  that is provided in opening  28   d  of mold plate  30   d  to maintain the nozzle head  90  in abutment with the lower surface  13  of manifold  12   d . Nozzle  20   d  further includes a nozzle tip  42   d  that is coupled to the nozzle  20   d  by a transfer seal  44   d.    
     Similar to the previous embodiments, manifold plug  22   d  is press fit into manifold bore  24   d  and includes a dowel  60   d  that is received in an aperture  74   d  of outwardly extending flange  76   d . The dowel  60   d  engages a recess  61   d  in manifold  12   d  to maintain the manifold plug  22   d  in a proper orientation in bore  24   d . The manifold plug  22   d  includes a valve disk  62   d  having an upper surface  64   d  in contact with a lower surface  66   d  of back plate  56   d . The valve disk  62   d  further includes a generally conical shaped body  68   d  that reduces in cross-sectional area between the upper surface  64   d  and a neck  70   d . A valve pin receiving bore  72   d  extends through the manifold plug  22   d  and joins the melt channel  26   d  of the manifold plug  22   d . A valve pin (not shown) is slidable through the valve pin receiving bore  72   d  to selectively seat in mold gate  48   d . The valve pin is actuated by an actuator (not shown) that is located in cavity  58   d  in back plate  56   d.    
     Referring to  FIG. 7 , another embodiment of an injection molding apparatus  10   e  is shown. This embodiment is similar to the embodiment of  FIG. 6 ; however, mold gate  48   e  is thermally gated. The injection molding apparatus  10   e  includes a nozzle  20   e  having a nozzle channel  46   e  for receiving melt from a manifold channel  14   e  of manifold  12   e . The nozzle  20   e  includes a nozzle head  90   e  having a flange  92   e . The flange  92   e  abuts a step  94   e  that is provided in opening  28   e  of mold plate  30   e  to maintain the nozzle head  90   e  in abutment with the lower surface  13   e  of manifold  12   e . Nozzle  20   e  further includes a nozzle tip  42   e  that is coupled to the nozzle  20   e  by a transfer seal  44   e.    
     Manifold plug  22   e  is press fit into manifold bore  24   e  and includes a dowel  60   e  that is received in an aperture  74   e  of outwardly extending flange  76   e . The dowel  60   e  engages a recess  61   e  in manifold  12   e  to maintain the manifold plug  22   e  in a proper orientation in the bore  24   d . A melt channel  26   e  extends through the manifold plug  22   e  to redirect the melt flow between the manifold melt channel  14   e  and a manifold outlet  18   e.    
     Manifold plug  22   e  includes a valve disk  62   e  having an upper surface  64   e  in contact with a lower surface  66   e  of back plate  56   e . A recess  78   e  is provided in upper surface  64   e  of the manifold plug  22   e , as shown in  FIG. 8 . An aperture  96  is also provided in upper surface  64   e . The aperture  96  is generally centered in the valve disk  62   e  and extends through neck  70   e  of the manifold plug  22   e . The recess  78   e  and the aperture  96  reduce the cross-sectional area of the valve disk  62   e  and increase the flexibility thereof to improve the deflection capability of the valve disk  62   e  during thermal expansion. The valve disk  62   e  further includes a generally conical shaped body  68   e  that reduces in cross-sectional area between the upper surface  64   e  and the neck  70   e.    
     The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.