Abstract:
A nozzle end is provided for removable mounting to a nozzle body for use in multiple-tipped molding applications such as edge-gated systems. The nozzle end is made of a highly thermally conductive material and is preferably inserted at least partially inside the forward end of the heated nozzle body. Removable nozzle tips are insertable in the front end of the nozzle end.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to injection molding and more particularly to an extension member for mounting to a heated multiple-tipped nozzle in a well in a mold. 
     BACKGROUND OF THE INVENTION 
     A key concern in injection molding is temperature of the pressurized melt as it passes through the runner system to the mold cavity. Thus, among other steps taken, the nozzle is usually heated, typically by an electrical element wrapped therearound. A difficulty arises, however, in the case of multiple-tipped nozzles, and particularly in the case of edge-gated nozzles, in that it is often difficult to extend the heating element all the way to the forward or mold end of the nozzle because it would interfere with the nozzle gating. Accordingly there is a need for a multiple-tipped injection molding nozzle offering improved temperature control adjacent the forward end of the nozzle. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention provides an injection molding apparatus comprising a plurality of mold cavities formed between at least one pair of mold plates, each cavity having a gate for communicating with an interior of the cavity, at least one injection molding nozzle body having a back end, a front end, at least one melt channel through the body and a heating member for heating the body, the at least one body capable of receiving heated pressurized melt from a source and capable of feeding the heated pressurized melt from the back end through the at least one melt channel to the front end, and a nozzle end mounted to the front end of the at least one body, the nozzle end having a bore therethrough extending from the melt channel at the body front end and communicating with at least two of the plurality of mold cavities, the nozzle end being made substantially of a material having a higher thermal conductivity than the at least one body. 
     In a second aspect, the present invention provides an improvement in an injection molding apparatus having at least one heated nozzle extending forwardly into a well in a mold, the well having a wall with a plurality of gates spaced therein, each gate extending to a cavity in the mold, the at least one nozzle having a rear end, a front end and a melt channel, the melt channel extending from an inlet at the rear end of the nozzle to an outlet at the front end of the nozzle, the improvement comprising a nozzle end mounted to the front end of the at least one nozzle, the nozzle end having a bore therethrough adapted to extend from the melt channel outlet at the front end of the nozzle and to communicate with the plurality of gates, the nozzle end being made substantially of a material having a higher thermal conductivity than the nozzle. 
     In a third aspect, the present invention provides an injection molding apparatus comprising at least one mold cavity formed between at least one pair of mold plates, the at least one cavity having a gate for communicating with an interior of the cavity, at least one injection molding nozzle body having a back end, a front end, at least one melt channel through the body and a heating member for heating the body, the at least one body capable of receiving heated pressurized melt from a source and capable of feeding the heated pressurized melt from the back end through the at least one melt channel to the front end, and a nozzle end mounted to the front end of the at least one body, the nozzle end having a bore threrethrough extending from the melt channel at the body front end and communicating with the at least one mold cavity, the bore having a portion extending substantially perpendicularly to the melt channel, the nozzle end being made substantially of a material having a higher thermal conductivity than the at least one body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example to the accompanying drawings. 
         FIG. 1  is a sectional view of a portion of an injection molding system incorporating a nozzle end according to an edge-gated embodiment of the present invention; 
         FIG. 2  is an enlarged sectional view of the nozzle end of  FIG. 1 ; 
         FIGS. 3a-3g  are enlarged sectional views of certain modifications available to the nozzle end of  FIG. 1 ; 
         FIG. 4  is an enlarged sectional view of a straight-gated embodiment of the nozzle end of the present invention; 
         FIGS. 5a-5c  are enlarged sectional views of certain modifications available to the nozzle end of  FIG. 4 ; 
         FIG. 6  is an enlarged sectional view of the nozzle end of  FIG. 4  according to a further alternate embodiment thereof; 
         FIG. 7a  is an enlarged sectional view of the nozzle end of  FIG. 1  according to a yet further alternate embodiment thereof; and 
         FIG. 7b  is a much enlarged view of the sealing means of the nozzle end of FIG.  7 a. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 2 , a portion of an edge gated injection molding system  10  having a nozzle end according to the present invention is shown. System  10  has a heated nozzle  12  in a well  14  in a mold  16 . System  10  also has a heated steel manifold  18  to distribute melt to several spaced nozzles  12  (only one of which is shown in FIG.  1 ), and each nozzle  12  distributes the melt to a plurality of spaced edge gates  20  leading to cavities  22 . While, in this example, each well  14  is defined in a support plate  24 , a nozzle mold plate  25 , a cavity plate  26  and an under cavity plate  27 , other arrangements of mold plates can be used if desired. 
     In this embodiment, each nozzle  12  has a nozzle extension member or nozzle end  28  with a rear portion  30  which extends a distance inside a nozzle body portion  32  of nozzle  12 . The distance by which rear portion  30  extends inside body  32  may be varied, as will be discussed further below. Nozzle end  28  is removably mounted to a seat  34  in nozzle body  32 , as will also be discussed further below. Nozzle  12  is heated by a electrical heating element  36  extending around nozzle body  32  and to an external terminal  38 . Nozzle body  32  has a thermocouple  40 , a support flange  42 , a forward end  44 , and a rear end  46 . 
     Melt distribution manifold  18  has an inlet  48 , adapted to communicate with an injection molding machine, and an electrical heating element  50 . A melt passage  52  extends from inlet  48  to each nozzle  12 , where it communicates with a nozzle melt channel  54  in nozzle body  32 . Melt channel  54  communicates with a bore  56  in nozzle end  28  which, in turn, communicates with tip channels  58  in a plurality of nozzle tips  60 . In this embodiment, tips  60  are tip edge gates adapted to deliver pressurized melt through melt gates  20  to cavities  22 . Manifold  18  is mounted between support plate  24  and a back plate  62 . Insulative and resilient spacer members  64  are located between manifold  18  and back plate  62  by pins (not shown). Bolts  68  which extend through the mold plates to hold them together apply a force through spacer members  64  to hold the manifold  18  and nozzles  12  securely in position. Bolts  70  which extend from manifold  18  into the mold also secure manifold  18  tightly against rear end  46  of the nozzle  12 . A central locating ring  72  is seated between manifold  18  and nozzle mold plate  25  to accurately locate the manifold in place. This provides an insulative air space  74  between heated manifold  18  and adjacent support plate  24 , nozzle mold plate  25  and back plate  62 . Cooling conduits  76  circulate water through cavity plate  26  and back plate  62  for cooling the mold. 
     Referring specifically to  FIG. 2 , nozzle end  28  contacts and abuts nozzle body  32  along an interface  80 . Nozzle end  28  has mounting means  82  for releasably mounting nozzle end  28  in seat  34  of nozzle body  32 . In this case, mounting means  82  comprises a mating thread set  84  in nozzle end  28  and seat  34 . Similarly, nozzle tips  60  have mounting means  86 , in this case thread sets  88 , for releasably mounting tips  60  to nozzle end  28 . Each nozzle tip  60  has a collar  90  which is preferably hexagonally-shaped and adapted to permit tip  60  to grasped by an appropriate tool for mounting and demounting tip  60  to nozzle end  28 . Tip  60  also has sealing means  92  for sealingly engaging the inner surface of well  14  around gate  20  to minimize leakage of pressurized melt into the space between well  14  and nozzle  12 . In this case, sealing means  92  comprises a flat flange or face  94  adapted to seat against the wall of the well  14 . 
     Nozzle end  28  is made of a highly thermally conductive material such as beryllium copper alloy or tungsten carbide. The material preferably has a thermal conductivity higher than that of steel. Nozzle body  32  may be of standard steel construction. Tips  60  are preferably made of a wear resistant material, such tungsten carbide, which advantageously also gives tips  60  good thermal conduction characteristics. 
     In use, injection molding system  10  is assembled as shown in FIG.  1 . Electrical power is applied to heating element  50  in manifold  18  and to heating elements  36  in nozzles  12  to heat them to a predetermined operating temperature. Some heat energy transferred from heating element  36  to nozzle body  32  is subsequently transferred by conduction across interface  80  to nozzle end  28 , and from nozzle end  28  to tips  60 . Thermocouple  40  provides temperature feedback to a controller. Once at operating temperature, pressurized melt from an injection molding machine (not shown) is injected into the melt passage  52  according to a controlled cycle. Pressurized melt passes from inlet  48 , through melt passage  52 , melt channel  54 , bore  56 , tip channels  58  and edge gates  20  to fill cavities  22 . After cavities  22  are filled, injection pressure is held momentarily to pack the molded products and then the pressure is released. After a short cooling period, the mold is opened to eject the molded products. After ejection, the mold is closed and injection pressure is reapplied to refill cavities  22 . This cycle is continuously repeated with a frequency dependent, inter alia, on the size and shape of the cavities and the type of material being molded. 
     The heat energy transferred to nozzle end  28  is, by nature of the highly conductive nature of the material of which the nozzle end is made, readily available to permit melt in bore  56  and tip channels  58  to be maintained at a desired temperature. Unlike the prior art, heat control is more accurately in the vicinity of the nozzle end, where the placement of external heaters is often not feasible due to gate and tip configuration constraints. The present invention also offers a simpler and more economical manner in which heat control can be achieved in the melt passage near the tips. 
     By extending inside nozzle body  32 , rear portion  30  provides an increased area to interface  80  over which heat energy may be transferred from heated nozzle body  32  to nozzle end  28 . Furthermore, as one skilled in the art will appreciate, rear portion  30  provides additional mass to nozzle end  28  thereby increasing the thermal regulating characteristics of the nozzle end. The length of rear portion  30  may be varied to extend to shorten the length of bore  56 , as required by the design of the particular system with which it is to be employed. 
     The system of the present invention may be used with any desired tip  60  style. Turning to  FIG. 3a , nozzle end  28  may be adapted for use with torpedo style tips  60 a, wherein sealing means  92 a comprises a nozzle seal sleeve  100  having a forward lip  102  adapted to engage the wall of well  14  to create a seal around gate  20 . In this embodiment, tips  60 a are arranged perpendicularly to bore  56 . Likewise, referring to  FIG. 3b , tips  60 b have sealing means  92 b comprising flat flanges  94 b and tips  60 b are arranged perpendicularly to bore  56 . Referring to  FIG. 3c , sealing means  92 c of tips  60 c comprise an integral circular flange  104  encircling gate  20  and adapted to sealingly engage the wall of well  14 . 
     The system of the present invention may employ various means of mounting nozzle end  28  to nozzle body  32 . Referring to  FIG. 3d , the location of mounting means  82 d is variable, and thread set  84 d may be moved closer to tips  60 d. Referring to  FIG. 3e , mounting means  82 e comprises brazing  108  along interface  80 e. Similarly, mounting means  86 e may comprise brazing  110 , if desired. Referring to  FIG. 3f , mounting means  82 f may comprise a thread set  84 f extending around the outside of nozzle body  32  between a flange  112  and nozzle body  32 . Interface  80 f may also be optionally brazed by brazing  108 f.  FIG. 3f  also demonstrates a nozzle  28  having a modified rear portion  30 f of decreased length, as previously discussed. Referring to  FIG. 3g , mounting means  82 g may comprise brazing  108 g and may also optionally comprise brazing  114  between flange  112 g and body  32 . In this embodiment, it is demonstrated that nozzle end  28 g may be adapted to permit thermocouple  40 g to extend at least partially therein to more accurately monitor the temperature of nozzle end  28 g. Thermocouple  40 g may be secured therein by copper alloy brazing  116 . 
     The nozzle end of the present invention may also be employed with other multiple nozzle tip configurations. It will be understood that in the following figures, reference numerals indicating elements similar to the system of  FIG. 1  are denoted by the same reference numerals. Referring to  FIG. 4 , a nozzle end  28  having a multi-tip straight gating configuration is shown. Here, tips  60  are aligned substantially parallel to bore  56  and substantially adjacent to one another. One skilled in the art will appreciate that the modifications of  FIGS. 3a-3g  are similarly available with this embodiment. Specifically,  FIG. 5a  shows mounting means  82  as brazing  108 ,  FIG. 5b  shows a flange  112  surrounding body  32  and having a thread set  84 , and  FIG. 5c  shows a flange  112  and wherein mounting means  82  comprises a braze  108  and a braze  114 . In this embodiment, it is also demonstrated that nozzle end  28  may be adapted to permit thermocouple  40  to extend at least partially therein to more accurately monitor the temperature of nozzle end  28 . Thermocouple  40  may be secured therein by copper alloy brazing. Referring again to  FIG. 5b , nozzle end  28  also incorporates a modified rear portion  30  of decreased length. 
     Although the present invention permits better heat control adjacent the nozzle tips without additional heaters, as shown in  FIG. 6  it may be desirable in certain instances to include an electrical heating element  118  around nozzle end  28  or, as shown in  FIG. 6 , integrally incorporated into nozzle end  28 . Element  118  may be separately controllable from element  36  and may be monitored independently by a second thermocouple  120 . The placement and configuration of heating element  118  is flexible depending on the requirements of the molding system. 
     Referring to  FIG. 7a , nozzle end  28  is adapted to receive a sealing ring  122  of the type described in U.S. Pat. No. 5,820,899 to Gellert et al., which is incorporated herein by reference. In this embodiment, circular sealing ring  122  extends around each nozzle to bridge the air space  124  between nozzle  12  and well  14  and to provide a seal against leakage of melt into well  14 . Sealing ring  122  is preferably made of an insulative material such as titanium alloy. Referring to  FIG. 7b , sealing ring  122  has a V-shaped front surface  126  and a rear end  128  which abuts against a circular shoulder  130  extending around nozzle end  28 . Thus, the sealing ring  122  forms a sealed portion  132  of air space  124  around nozzle  12 . The outer end  134  of nozzle tip  60  is spaced from the wall of the well  14  at a predetermined distance “D” to form an opening  136  between them. Pressurized melt flows outwardly through this opening  92  during the initial injection cycle and partially solidifies in sealed portion  132  of air space  124 . Distance “D” is made large enough to allow the melt to initially flow outwardly therethrough, but small enough to prevent the partially solidified melt in sealed portion  132  of air space  124  being sucked back into the melt stream flowing into the cavity  22  during subsequent injection cycles. In the embodiment shown, the distance “D” is preferably approximately 0.1 millimeters, although the distance can be varied depending upon the characteristics of the material being molded. 
     While the description of the present invention has been given with respect to a preferred embodiment, it will be evident that various modifications are possible without departing from the scope of the invention as understood by those skilled in the art and as defined in the following claims.