Abstract:
An injection molding machine and injection nozzle having a plurality of nozzle tips affixed to a single nozzle bushing is shown.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to injection molding nozzles. More particularly, this invention relates to a multi-tip injection-molding nozzle, which provides reduced pitch spacing between each nozzle tip.  
           [0003]    2. Summary of the Prior Art  
           [0004]    Injection molding is widely used for the manufacture of a variety of items, some of which have thin and delicate cross sections. These items can be molded in large quantities by using a single heated nozzle that extends into a single mold bore which feeds a number of mold cavities. These mold cavities typically have gates which extend through the mold block between the mold bore and the mold cavity, forming a melt flowpath to convey the injected melt from the bore to the mold cavities. Multi-tip nozzles are known in practice and serve in particular to enable relatively small parts to be molded in multiple injection molding molds in a narrow space in order that the multiple mold can be used as well as possible. The individual openings of the multi-tip nozzles can be so closely arranged relative to one another because of their common drive and their arrangement in a common housing so that even small workpieces and their mold cavities can be arranged in the multiple mold correspondingly close to one another.  
           [0005]    As seen in U.S. Pat. No. 4,094,447, (incorporated herein by reference) a heated nozzle in which the melt passage branches outwardly to several edge gates is provided. While this is suitable for edge gating, each of the front portions of the nozzle has a flat face which is not suitable for hot tip gating.  
           [0006]    U.S. Pat. No. 4,921,708 (incorporated herein by reference) shows a multi-gate application with hot tips provided by four elongated probes mounted around a heated nozzle. Other arrangements of multi-tip nozzles are also well known. However, they all require the use of a specially adapted nozzle bushing and take up more space than a typical single tip nozzle. In a system with a large number of gates, it is usually preferable to reduce overall size by having the gates as close together as possible.  
           [0007]    Another previous construction of a heated multiple gate nozzle which directs the melt to multiple mold gates is shown in Canadian Pat. No. 976,314, (incorporated herein by reference) in which a multi-gate heater is disclosed having an intricately milled nozzle face with a series of convex openings formed therein.  
           [0008]    Another construction such as that shown in U.S. Pat. No. 4,094,447 (incorporated herein by reference) relies in part on a specific configuration of the mold bore which includes a raised portion of the bore which is generally complementary to the heater nozzle face to fill much of the open area in the bore to cut down on the amount of heat transferred to the mold block during operation. Such approaches require costly machining of both the heater ends and mold bore.  
         SUMMARY OF THE INVENTION  
         [0009]    The primary objective of the present invention is to provide a multi-tip injection molding system with substantially smaller spacing between the tips of the nozzle.  
           [0010]    Another object of the present invention is to provide a hot tip injection nozzle having an increased number of injection gates from a single nozzle body.  
           [0011]    Still another object of the present invention is to provide a multi-tip plate that may be easily adapted to an existing injection nozzle.  
           [0012]    Yet another object of the present invention is to provide a means for maximizing the available space of a mold by molding very small parts in a tightly packed arrangement.  
           [0013]    The foregoing objects are achieved by providing an injection molding system that comprises a multi-tip injection molding nozzle. The multi-tip injection molding nozzle comprises a distribution plate with a plurality of nozzle tips affixed thereon. The distribution plate is rigidly affixed to a distal end of the injection nozzle. In this arrangement, a single nozzle assembly can provide a plurality of gates in a tightly spaced array for the production of large quantities of molded articles.  
       
    
    
       [0014]    Further objects and advantages of the present invention will appear hereinbelow.  
       BREIF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a simplified cross-sectional view of an injection molding nozzle in accordance with the present invention;  
         [0016]    [0016]FIG. 2 is a bottom plan view of the distribution plate having a plurality of nozzle tips;  
         [0017]    [0017]FIG. 3 is a top plan view of the distribution plate showing a plurality of melt flow channels feeding a plurality of nozzle tips;  
         [0018]    [0018]FIG. 3 a  is a simplified cross-sectional view of the distribution plate with the second melt channel being formed in the distribution plate;  
         [0019]    [0019]FIG. 4 is a cross-sectional view of another preferred embodiment in accordance with the present invention where the distribution plate is formed integral to the retaining device for attachment to a nozzle;  
         [0020]    [0020]FIG. 5 is a cross-sectional view of another preferred embodiment in accordance with the present invention where the distribution plate is formed integral to the retaining device for attachment to a nozzle;  
         [0021]    [0021]FIG. 6 is a bottom plan view of the distribution plate that comprises threaded fasteners to affix the plate to a nozzle.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring first to FIG. 1, a simplified cross-sectional view of an injection nozzle in accordance with a preferred embodiment  10  of the present invention is generally shown. A nozzle bushing  16  is inserted into a cavity  32  of a manifold plate  36 . An insulator  28  is provided in cavity  32  to support the nozzle bushing  16  thereby reducing thermal communication of nozzle bushing  16  to manifold plate  36 . A spring  30  is inserted between nozzle bushing  16  and insulator  28  to provide a sealing force to resist leakage of molten material as it flows from a hot runner channel  42  of a hot runner manifold  40  to a first melt channel  18  running along a longitudinal axis of nozzle bushing  16 .  
         [0023]    Rigidly affixed to the lower distal end of nozzle bushing  16  by a fastener  14  is a distribution plate  12  for the communication of molten material from first melt channel  18  to a plurality of second melt channels  20 . A plurality of nozzle tips  22  each preferably having a nut shaped portion  21 , are rigidly affixed to distribution plate  12  adjacent a plurality of gates  38 . An equal number of third melt channels  24  communicate the molten material from second melt channels  20  to each nozzle tip  22 . The molten material is then communicated through each nozzle tip  22  to a respective gate  38  and then into a mold cavity (not shown) for the formation of a molded article.  
         [0024]    Optionally, a locating device  34  is affixed between nozzle body  16  and distribution plate  12  to maintain the alignment of second melt channels  20  to third melt channels  24 . A heater  26 , well known in the art, is in thermal communication with the nozzle body  16  for maintaining the temperature of the molten material at a predetermined level.  
         [0025]    Referring to FIG. 2, a bottom view of distribution plate  12  is shown. A plurality of nozzle tips  22   a - 22   d  are rigidly affixed in a predetermined pattern to a bottom surface of distribution plate  12 . In a preferred embodiment, the nozzle tip  22  is threaded into a threaded hole located in the distribution plate  12 , but other suitable attachment means are also contemplated.  
         [0026]    Referring now to FIGS. 3 and 3 a,  an alternate embodiment of the distribution plate  12  is shown where second melt channels  20  are formed integral to the distribution plate  12  rather than as part of the nozzle bushing  16 . As shown, a plurality of second melt channels  20  extend from a central point of distribution plate  12  to each nozzle tip location. Using this arrangement, a given nozzle bushing  16  would not need to be replaced if the number of nozzle tips  22  were to be changed. Only the distribution plate  12  would need modification to accommodate a different number or layout of nozzle tips  22 .  
         [0027]    Referring now to FIG. 4, where like features have like numerals, an alternative embodiment according to the present invention is shown. In this embodiment, the distribution plate  12  comprises threads, so that it may be mounted on a distal end of the nozzle bushing  16  without the use of the previously described fastener  14 . In this arrangement, the ability to align second melt channel  20  to third melt channels  24  has been eliminated, but if second melt channels  20  are formed in distribution plate  12  as shown in FIG. 3 and  3   a,  maintaining alignment is unnecessary.  
         [0028]    Referring now to FIG. 5, another preferred embodiment of the present invention is shown. In this embodiment, the configuration of the distribution plate  12  has been modified to comprise external threads at a top distal end for insertion into receiving threads located at a bottom distal end of nozzle bushing  16 . A longitudinal melt channel  18 a has been added to the distribution plate  12  to communicate the molten material from first melt channel  18  to second melt channel  20 .  
         [0029]    Referring to FIG. 6, yet another preferred embodiment of the present invention is shown. In this embodiment, the distribution plate  12  is mounted to nozzle bushing  16  by a plurality of threaded fasteners  44 . Each fastener  44  is inserted into a threaded hole in the lower distal end of the nozzle bushing  16 . The number of fasteners  44  required is determined by the sealing force required to preclude leakage of high pressure molten material between the distribution plate  12  and nozzle bushing  16 .  
         [0030]    It is to be understood that the invention is not limited to the illustrations described herein, which are deemed to illustrate the best modes of carrying out the invention, and which are susceptible to modification of form, size, arrangement of parts and details of operation. The invention is intended to encompass all such modifications, which are within its spirit and scope as defined by the claims.