Abstract:
Injection molding apparatus having a cavity insert ( 10 ) with integral inner and outer portions ( 136, 138 ) having a cooling fluid flow channel ( 166 ) extending therebetween. In a preferred embodiment, the cooling fluid flow channel ( 166 ) is formed by a groove ( 164 ) machined in the outer surface ( 162 ) of the inner portion ( 136 ). This brings the cooling fluid flow closer to the cavity ( 66 ) and improves cooling efficiency and reduces cycle time.

Description:
BACKGROUND OF THE INVENTION 
     This application relates generally to injection molding apparatus and more particularly to injection molding apparatus having a cavity insert with a cooling fluid flow channel therein. 
     Injection molding apparatus having cooling fluid channels or conduits are well known. For instance, the applicant&#39;s U.S. Pat. No. 5,427,519 which issued Jun. 27, 1995 shows a thermal setting application wherein a cooling fluid channel extends around a central liquid molding material channel in a nozzle. The applicant&#39;s U.S. Pat. No. 5,443,381 which issued Aug. 22, 1995 shows hot runner apparatus having cooling fluid conduits extending through a gate insert. Canadian Patent Application Serial Number 2,228,931 filed Feb. 2, 1998 by Mold-Masters Limited is another example of a gate insert having helical cooling fluid conduits or passages. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to at least partially overcome the disadvantages of the prior art by providing a cavity insert with inner and outer portions integrally joined together with a cooling fluid flow channel extending between the inner and outer portions. 
     To this end, in one of its aspects, the invention provides injection molding apparatus having a cavity with an outer surface extending in a mold and a hollow cavity insert having an inner surface mounted in the mold, wherein the inner surface of the cavity insert forms the outer surface of the cavity. The cavity insert has a hollow inner portion and a hollow outer portion integrally joined together. The outer portion has an inner surface and the inner portion has an outer surface. The inner portion fits inside the outer portion with the outer surface of the inner portion adjacent the inner surface of the outer portion. Either the outer surface of the inner portion or the inner surface of the outer portion has a groove therein to form a cooling fluid flow channel extending between the inner portion and the outer portion. The cooling fluid flow channel extends from a cooling fluid inlet to a cooling fluid outlet in a predetermined configuration around the cavity. 
     Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a portion of a multi-cavity injection molding system showing a cavity insert according to a preferred embodiment of the invention, 
     FIG. 2 is an exploded isometric view showing the three portions of the cavity insert seen in FIG. 1 in position for assembly, and 
     FIG. 3 is a sectional view of the cavity insert seen in FIG. 2 with the three portions integrally joined together. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is first made to FIG. 1 which shows a portion of a multi-cavity injection molding system or apparatus used for molding beverage bottle preforms having an elongated fluid cooled hollow cavity insert  10  according to a preferred embodiment of the invention. In this configuration, a number of heated nozzles  12  are mounted in openings  14  in a mold  16  with the rear end  18  of each heated nozzle  12  abutting against the front face  20  of a steel melt distribution manifold  22 . Each nozzle  12  is heated by an integral electrical heating element  24  and has a thermocouple element  26  extending into its front end  28  to monitor and control the operating temperature. Each heated nozzle  12  has a cylindrical locating flange  30  seated in a circular locating seat  32  in the opening  14 . This provides an insulative air space  34  between the heated nozzle  12  and the surrounding mold  16 , which is cooled by pumping cooling water through cooling conduits  36 . 
     The melt distribution manifold  22  is also heated by an integral electrical heating element  38 . The melt distribution manifold  22  is mounted between a manifold plate  40  and clamp plate  42  which are secured together by bolts  44 . The melt distribution manifold  22  is located by a central locating ring  46  and a number of insulative spacers  48  which provide an insulative air space  50  between it and the surrounding cooled mold  16 . 
     A melt passage  52  extends from a central inlet  54  in an inlet portion  56  of the melt distribution manifold  22  and branches in the melt distribution manifold  22  to extend through a central melt bore  58  in each of the heated nozzles  12 . The melt passage  52  extends through a two-piece nozzle seal  60  aligned with a gate  62  extending through a cooled gate insert  64  to an elongated cavity  66 . This cavity  66  for making beverage bottle preforms extends between the cavity insert  10  and thread split inserts  68  on the outside and a cooled mold core  70  on the inside. The gate insert  64  and the cavity insert  10  are seated in an opening  72  in a cavity plate  74  through which cooling water lines  76  extend to the cooled gate insert  64 . 
     The cooled mold core  70  has an elongated hollow inner part  78  extending inside an elongated hollow outer part  80 . The mold core  70  has an outer surface  82  extending from a dome shaped front end  84  to a rear end  86 . The outer surface  82  of the elongated mold core  70  has a front portion  88  and a rear portion  90 . The front portion  88  forms the inner surface  92  of the cavity  66 , and the rear portion  90  extends rearwardly from the cavity  66  through an opening  94  through a core lock member  96  which is secured to a core backing plate  98  by bolts  100 . The core lock member  96  in turn extends through an opening  102  through a slide member  104  and a wear plate  106  which is secured to a stripper plate  108  by screws  110 . Cooling fluid supply and return lines  112 ,  114  extend in the core backing plate  98  and are connected respectively to a central cooling fluid duct  116  extending longitudinally through the inner part  78  and a cylindrical outer cooling fluid duct  118  extending between the inner part  78  and the outer part  80  of the mold core  70 . 
     The rear portion  90  of the outer surface  82  of the mold core  70  has a tapered part  120  which tapers inwardly towards the rear end  86  of the mold core  70 . As can be seen, the opening  94  through the core lock member  96  has an inner surface  122  with a tapered part  124  which also tapers inwardly towards the rear end  86  of the mold core  70  and matches the tapered part  120  of the rear portion  90  of the outer surface  82  of the mold core  70 . The rear portion  90  of the outer surface  82  of the mold core  70  also has a threaded part  126  onto which a cylindrical nut  128  is screwed. The nut  128  is seated in a seat  130  in the rear face  132  of the core lock-member  96  and is tightened by a spanner wrench which fits in holes  134  to secure the mold core  70  to the core lock member  96  with the tapered part  120  of the outer surface  82  of the mold core  70  abutting against the matching tapered part  124  of the inner surface  122  of the opening  94  through the core lock member  96 . 
     Also referring to FIGS. 2 and 3, the cavity insert  10  has an elongated hollow inner portion  136 , an elongated hollow outer portion  138 , and a base portion  140 . The outer portion  138  has an outer surface  142  and a cylindrical inner surface  144 . As can be seen, the outer surface  142  tapers inwardly towards the front and fits in the matching tapered opening  72  extending through the cavity plate  74 . The outer portion  138  also has a rear end  148  which fits in a circular seat  150  in the base portion  140 . The base portion  140  has holes  152  through which screws  154  extend into holes  156  in the cavity plate  74  to secure the cavity insert  10  in place. 
     In this embodiment, the inner portion  136  of the cavity insert  10  has a cylindrical inner surface  158  which forms the outer surface  160  of the cavity  66  and an outer surface  162  with a groove  164  therein which fits inside the outer portion  138 , with the outer surface  162  of the inner portion  136  adjacent the inner surface  144  of the outer portion  138 . The groove  164  in the outer surface  162  of the inner portion  136  extends in a predetermined configuration to form a cooling fluid flow channel  166  extending between the inner portion  136  and the outer portion  138  from a cooling fluid inlet  168  and a cooling fluid outlet  170 , both of which extend through the outer portion  138  to supply and return lines  172 ,  174  respectively in the cavity plate  74 . In this embodiment, the outer portion  138  of the cavity insert  10  is longer than the inner portion  136  to also receive the gate insert  64  therein. 
     Reference is now made to FIGS. 2 and 3 in describing the method of making the cavity insert  10  according to the invention. First, the inner portion  136 , the outer portion  138  and the base portion  140  seen in FIG. 2 are machined of steel with the groove  164  shaped to provide turbulent flow extending in the outer surface  162  of the inner portion  136 . Then, a bead of nickel alloy brazing paste is applied around the circular seat  150  in the base portion  140 , and the inner portion  136 , the outer portion  138  and the base portion are assembled as seen in FIG.  3 . Another bead of nickel alloy brazing paste is applied around the front end  176  of the inner portion  136 . The assembled inner portion  136 , outer portion  138  and base portion  140  are then gradually heated in a vacuum furnace to a temperature of approximately 1925° F. which is above the melting point of the nickel alloy. As the furnace is heated, it is evacuated to a relatively high vacuum to remove substantially all of the oxygen and then partially backfilled with an inert gas such as argon or nitrogen. When the melt point of the nickel alloy is reached, it melts and flows by capillary action between the inner and outer portions  136 ,  138  and the base portion  140  to integrally braze the three portions together to form the integral one-piece cavity insert  10  shown in FIG.  3 . Brazing them together this way in the vacuum furnace provides a metallurgical bonding between them to maximize the strength of the cavity insert  10  and prevent leakage of the cooling fluid from the cooling fluid flow channel  166 . 
     In use, after the system has been assembled as shown in FIG. 1, electrical power is applied to the heating elements  24 ,  38  to heat the nozzles  12  and the melt distribution manifold  22  to a predetermined operating temperature. A suitable cooling fluid such as water is also circulated by pumps (not shown) through the cooling conduits  36  in the mold  16  and the lines  76  in the cavity plate  74  leading to the gate inserts  64 . Usually a cleaner cooling fluid such as glycol is pumped in closed loop cooling systems through the supply and return lines  112 ,  114  to circulate through the mold cores  70  and through the supply and return line  172 ,  174  to circulate through the cavity inserts  10 . Pressurized melt from a molding machine (not shown) is then introduced according to a predetermined injection cycle into the central inlet  54  of the melt passage  52  of the melt distribution manifold  22 , from where it flows through the central melt bore  58  in each of the heated nozzles  12  and the two-piece nozzle seals  60  and through the gates  62  to fill the cavities  66 . After the cavities  66  are full, injection pressure is held momentarily to pack and then released. After a short cooling period, the mold  16  is opened to eject the product. After ejection, the mold  16  is closed and the injection pressure is reapplied to refill the cavity  66 . This cycle is repeated continuously with a cycle time dependent upon the size of the cavities  66  and the type of material being molded. 
     While the description of the cooled cavity insert  10  having a cooling fluid flow channel  166  extending between integral inner and outer portions  136 ,  138  has been given with respect to a preferred embodiment, it will be evident that various other modifications are possible without departing from the scope of the invention as understood by those skilled in the art and as provided in the following claims.