Abstract:
A nozzle adapter for an injection molding machine includes a body and one or more retainers mountable to an outer surface of the body. When the body and a retainer are assembled together they cooperate to define a cavity adapted to contain a cartridge heater between the body and the retainer. Access to allow replacement of the cartridge heater can be gained by removing the retainer from the body without removing the entire nozzle adapter from the injection molding machine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/066,691, filed Feb. 22, 2008, which is incorporated by reference. 
    
    
     TECHNICAL FIELD OF INVENTION 
     This invention relates to injection molding machines, and in particular to nozzle adapters for injection molding machines. 
     BACKGROUND OF THE INVENTION 
     Injection molding is a process in which a molding machine forces melted plastic through a nozzle into a mold cavity where it is held until it solidifies, resulting in a solid part that assumes the shape defined by the cavity. Before injection into the mold, the plastic must be heated to a temperature which allows it to flow under pressure. Molding machines may use a nozzle adapter that defines a melt passage to convey molten plastic from the machine through the nozzle to the mold. It is important to keep the molten material at the proper temperature to optimize the flow of the material into the mold. To achieve and maintain the proper temperature of the material injected into the mold, one or more heaters may be used to heat the nozzle adapter. Currently available nozzle adapters often contain one or more electrically powered cartridge heaters located parallel to the melt passage. In such conventional configurations a cartridge heater is commonly inserted into a circular hole accessed through an end of the nozzle adapter. 
     For best heater efficiency it is desirable for the outside diameter of the heater to closely match the diameter of the hole into which the heater is inserted. For this reason, it is common to ream the hole to achieve close dimensional tolerances. The conventional method of inserting the heater into a hole requires that the hole diameter be large enough to accommodate a slip fit, which may result in reduced heater efficiency. In the event a heater needs to be replaced, material galling or sticking may make it difficult to extract a heater from a tight cylindrical passageway. It may be necessary to drill out a defective heater from a nozzle adapter, resulting in the potential of damaging the nozzle adapter. For example, the process of drilling out a cartridge heater may result in enlargement of the hole, so that heat transfer between the nozzle adapter and the replacement heater is degraded. 
     In the conventional configuration described above it is necessary to be able to access the nozzle adapter from its end in order to replace a heater. In a typical injection molding machine, accessibility of the ends of a nozzle adapter requires complete removal of the nozzle adapter from the molding machine. This process is time consuming and may lead to extended machine downtime. 
     There is a need for an apparatus to contain cartridge heaters in a nozzle adapter that facilitates simplified, more convenient, and reliable replacement of one or more heaters with reduced machine downtime and reduced risk of damaging other components. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment of the invention, a nozzle adapter for an injection molding machine includes a body and one or more retainers mountable to an outer surface of the body. When the body and a retainer are assembled together they define a cavity adapted to contain a cartridge heater between the body and the retainer. Access to allow replacement of the cartridge heater can be gained by removing the retainer from the body without removing the entire nozzle adapter from the injection molding machine. Additionally, a cartridge heater can be replaced by accessing the nozzle adapter from a side, which typically offers an advantage over requiring access to an end of the nozzle adapter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an exploded view of an internally heated nozzle adapter according to an exemplary embodiment of the invention. 
         FIG. 2  is an end view of an internally heated nozzle adapter according to an exemplary embodiment of the invention. 
         FIG. 3  is a cross-sectional view, taken through  FIG. 2 , of an internally heated nozzle adapter according to an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     In accordance with an exemplary embodiment of the invention,  FIG. 1  shows an exploded view of an internally heated nozzle adapter  100 . The nozzle adapter  100  has a first end  14  adapted to mount to a molding machine  110 , and a second end  16  adapted to mount to a nozzle  120  that interfaces with a mold (not shown). In the embodiment shown in  FIG. 1 , the nozzle adapter  100  comprises a body  10 , which defines a melt passage  12  extending from the first end  14  to the second end  16 . When the nozzle adapter  100  is in use, the melt passage  12  is adapted to convey melted plastic from the molding machine  110  to the nozzle  120 . 
     In the embodiment shown in  FIG. 1 , the body defines a plurality of grooves on the outside surface, wherein each groove  18  is adapted to receive a cartridge heater  24 . The embodiment in  FIG. 1  contains three such grooves  18 , to accommodate three cartridge heaters  24 . The body  10  is preferably made of metal. 
       FIG. 1  also shows a set of heater retainers  20 . Each retainer  20  has a groove  22  that, when mounted to the nozzle adapter body  10 , cooperates with the groove  18  in the nozzle adapter body  10  to define a cavity that can retain a cartridge heater  24 . In the embodiment shown, the grooves  18  in the body  10  and the grooves  22  in the retainer  20  are each semicircular in cross section, and each body groove  18  is disposed so that when a retainer  20  is assembled to the body  10 , a body groove  18  is aligned with a retainer groove  22  to receive a cylindrical heater  24 . Three retainers  20  are shown, corresponding to the three grooves in the body  10  shown in  FIG. 1 . A retainer  20  can be made of metal or of an insulating material. 
     In the embodiment presented in  FIG. 1  the nozzle adapter body  10  and the retainer  20  are adapted to be fastened together by at least one screw  26  passing through a clearance hole  28  in the retainer  20  and engaging a tapped hole  30  in the body  10 . The retainer  20  could alternatively be attached to the body  10  by other fastening means, including but not limited to pins, studs, band clamps, toggle clamps, and other suitable means known in the art. 
       FIG. 1  also shows open regions  40  defined in the retainers  20  and open regions  41  defined in the body  10 . These open regions  40 ,  41  cooperate to define an opening that allows the wire leads of cartridge heaters  24  to exit the nozzle adapter  100 , for connection to appropriate heater control equipment. In alternative embodiments, the openings to accommodate the leads associated with cartridge heater could be defined wholly by body  10 , wholly by retainer  20 , or by both body  10  and retainer  20  as depicted in  FIGS. 1 and 3 . 
     Referring again to  FIG. 1 , the nozzle adapter body  10  can also define a passage  32  to receive a thermocouple  34  to monitor the temperature of the nozzle adapter  100 . In the embodiment shown, the body  10  also defines two openings  42  and  44  that extend from the exterior of body  10  to thermocouple passage  32 . Thermocouple  34  can be installed in body  10  by inserting the thermocouple  34  through opening  42 . The thermocouple  34  can then be pushed through passage  32  until it reaches opening  44 . Opening  44  provides visual and physical access to the thermocouple  34 , allowing it to be positioned so that it can be captured by set screw  36  installed in hole  38 . Opening  42  allows the thermocouple wires to exit the nozzle adapter for connection to appropriate temperature measurement and control equipment. 
       FIG. 2  shows an end view of an assembled nozzle adapter  100 , as seen from second end  16  of body  10 , according to an exemplary embodiment of the invention. In this embodiment, the nozzle adapter  100  is shown to have a cross section corresponding to a regular hexagon. This facilitates installation of the nozzle adapter  100  to the molding machine  110  shown in  FIG. 1 , as well as installation of the nozzle  120  shown in  FIG. 1  to the nozzle adapter  100 , using standard tools such as wrenches. The view in  FIG. 2  also clearly shows the grooves  18  in body  10  cooperating with the grooves  22  in retainer  20  to define a cavity adapted to receive cylindrical cartridge heaters  24 . In the embodiment shown, thermocouple passage  32  is formed by drilling into body  10  from second end  16  in a direction toward first end  14 . 
       FIG. 3  is a cross section of nozzle adapter  100  in the direction indicated in  FIG. 2 .  FIG. 3  shows more clearly melt passage  12  extending through body  10  from the first end  14  to the second end  16 .  FIG. 3  also more clearly shows thermocouple  34  installed in passage  32  and captured by set screw  36 . Opening  44  extends from the surface of body  10  to passage  32 , and is operable to provide access to assist in verifying the presence and location of thermocouple  34 , as well as access to allow urging thermocouple  34  to the desired location. The wire leads associated with thermocouple  34  exit the nozzle adapter  100  through opening  42 , which extends from the surface of body  10  to passage  32 . 
       FIG. 3  also shows a cartridge heater  24  installed in the cavity defined by the cooperation of groove  18  in body  10  and groove  22  in retainer  20 . The wire leads associated with cartridge heater  24  exit the nozzle adapter  100  through an open region defined by the cooperation of opening  40  defined in retainer  20  and opening  41  defined in body  10 . In alternative embodiments, the opening to accommodate the leads associated with cartridge heater could be defined wholly by body  10 , wholly by retainer  20 , or by both body  10  and retainer  20  as depicted in  FIGS. 1 and 3 . 
     Access to a defective heater for the purpose of repairing or replacing the heater can be gained by removing the corresponding retainer. Removal and replacement of component parts from the heated nozzle adapter can be accomplished by access in an essentially radial direction. This may allow repair or replacement of a heater to be accomplished without removing the nozzle adapter from the molding machine. With the retainer removed from the body, a heater is easily removed, compared to removing a heater axially from a tight cylindrical passageway. Heater replacement can be accomplished with reduced effort, reduced machine downtime, and decreased chances of damage to the nozzle adapter compared to conventional heated nozzle adapters in which heaters are installed in and removed axially from a cylindrical passageway. 
     While this invention has been described in terms of exemplary embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.