Abstract:
An ejector assembly for use with a mold for molding plastic parts include a first stationary member, a second stationary member and an ejector plate moveable between the first and second stationary members. A core blade lifter is provided that includes a lifter foot assembly that is moveable with the ejector plate. The core blade lifter includes a lifter rod pivotally mounted to the lifter foot assembly and moveable laterally and longitudinally in response to movement of the ejector plate. A stationary helper pin is provided generally parallel to the lifter rod. The core blade lifter includes a helper carrier pivotally mounted to the lifter foot assembly and moveable along the helper pin.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from U.S. provisional patent application Ser. No. 60/481,567 filed on Oct. 27, 2003, the disclosure of which is hereby incorporated herein by reference in its entirety. 

   BACKGROUND OF INVENTION 
   The present invention is directed to an ejector assembly for use with a mold for molding plastic parts and, in particular, to a lifter foot assembly for removal of a core block from the mold. 
   When molding a plastic part having an undercut feature underneath the part, it is necessary to eject the part from the mold in a compound motion. The motion involves lateral movement as well as movement away from the mold surface. This may be accomplished by a core blade lifter in the form of a lifter rod which is mounted at an angle to the ejector plate by a lifter foot assembly that is capable of traveling laterally along the ejector plate. This allows the ejector plate end of the lifter rod to move laterally as the ejector plate is actuated. 
   For certain part designs, the amount of undercut requires that the lifter rod be mounted at a more extreme angle with respect to the direction of movement of the ejector plate. Such extreme angle places additional force on the foot assembly which could result in failure or excessive wear to the lifter rod and/or the lifter foot assembly. 
   Designing an ejector assembly has traditionally been a time-consuming task. The lifter foot assembly has to be machined to accommodate the angle of the lifter rod. Moreover, if it desired to control the acceleration of the lifter rod during the ejection of the part, it is common to provide a slight increase or decrease in elevation up the lifter rod with respect to the ejector plate during the lateral motion of the lifter rod. This also must be calculated and specifically machined into the lifter foot assembly. 
   SUMMARY OF INVENTION 
   The present invention provides a universal lifter foot assembly and ejector assembly utilizing a universal lifter foot assembly which may be readily adapted to various applications without the need for custom machining. The universal lifter foot assembly and ejector assembly, according to the invention, is capable of accommodating increased lifter rod angles while reducing wear on the lifter rod and lifter foot assembly. The present invention accommodates the use of a helper pin in a manner which may be universally accommodated for various lifter rod angles and facilitates the crafting of acceleration of the lifter rod for particular applications. 
   An ejector assembly for use with a mold for molding plastic parts, according to another aspect of the invention, includes a first stationary member, a second stationary member and an ejector plate moveable between the first and second stationary members. A core blade lifter is provided that includes a lifter foot assembly that is moveable with the ejector plate and a lifter rod. The lifter foot assembly includes a rod carrier pivotally mounting the lifter rod to the lifter foot assembly. A stationary helper pin is provided that is generally parallel to the lifter rod. The core blade lifter includes a helper carrier that is pivotally mounted to the lifter foot assembly and is moveable along the helper pin. The lifter foot assembly includes a pair of gib plates with camming surfaces defined along the gib plates. The helper carrier and the rod carrier are commonly slidable along the camming surfaces. 
   A universal lifter foot assembly for use with an ejector assembly of a mold for molding plastic parts, according to another aspect of the invention, includes a pair of gib plates with camming surfaces defined along the gib plates. A carrier assembly is slidable with respect to the camming surfaces. The carrier assembly includes a rod carrier, a helper carrier and wear plates. The rod carrier and the helper carrier are pivotally mounted by the wear plates. The wear plates engage the camming surfaces. The rod carrier is adapted to actuate a lifter rod. The helper carrier is adapted to slide along a stationary helper pin generally parallel to the lifter rod. 
   A universal lifter foot assembly for use with an ejector assembly of a mold for molding plastic parts, according to another aspect of the invention, includes a pair of gib plates with camming surfaces defined along the gib plates. A carrier assembly is slidable with respect to the camming surfaces. The carrier assembly includes a rod carrier, a helper carrier and wear plates. The rod carrier and the helper carrier are pivotally mounted by the wear plates. The wear plates engage the camming surfaces. The rod carrier is adapted to actuate a lifter rod. The helper carrier is adapted to slide along a stationary helper pin generally parallel to the lifter rod. 
   These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a perspective view of a core blade lifter assembly, according to an embodiment of the invention, taken from the top, front, and right side thereof; 
       FIG. 2  is a perspective view of the core blade lifter assembly of  FIG. 1  taken from a bottom, front, and left side thereof; 
       FIG. 3  is a side elevation of the core blade lifter assembly of  FIG. 1  taken from the rear thereof; 
       FIG. 4  is an exploded perspective view of a lifter foot assembly, according to an embodiment of the invention; 
       FIGS. 5   a  and  5   b  are perspective views of a helper carrier; 
       FIGS. 6   a  and  6   b  are perspective views of a rod carrier; 
       FIGS. 7   a  and  7   b  are perspective views of an adjustment screw; and 
       FIGS. 8   a – 8   d  are side elevations of an ejector assembly illustrating operation thereof. 
   

   DETAILED DESCRIPTION 
   References to up, down, left, right, front, back, and the like, are for relative relational purposes only and should not be considered limiting unless specifically set forth. 
   Referring now specifically to the drawings, and the illustrative embodiments depicted therein, an ejector assembly  10  includes a top stationary member, or ejector block,  12 , a bottom stationary member, or clamp plate,  14  and an ejector plate  16  which is moveable between the clamp plate and the ejector block ( FIGS. 8   a–   8   d ). In order to eject a part from the mold (not shown), ejector plate  16  moves from a position generally adjacent the clamp plate in a direction of the ejector block. As is known in the art, ejector block  12  typically defines half of the mold, with the remaining portion of the mold defined by another mold half which is not shown. 
   Lifter foot assembly  22  includes symmetrical mirror image gib plates  28   a,    28   b  and a carrier assembly  30  which is slidable along camming surfaces  32   a,    32   b  defined in respective gib plates  28   a,    28   b  ( FIGS. 1–4 ). Carrier assembly  30  includes a rod carrier  34  that is adapted to engage and actuate lifter rod  20 . Carrier assembly  30  additionally includes a helper carrier  36  which captures and slides along upper pin  26 . Both rod carrier  34  and helper carrier  36  are pivotal with respect to gib plates  28   a,    28   b.  This may be accomplished by a pair of wear plates  38  which pivotally support the rod carrier and the helper carrier and which slidably engage camming surfaces  32 . Wear plates  38  include openings which rotatably support hubs  39  extending from rod carrier  34  and helper carrier  36 . In the illustrative embodiment, gib plates  28   a,    28   b,  rod carrier  34  and helper carrier  36  are made from steel and wear plates  38  are made from a self-lubricating material, such as bronze. However, other combinations of materials may be utilized as would be apparent to those skilled in the art. 
   Helper carrier  36  includes a through opening  40 , which is sized to slide along helper pin  26 . Rod carrier  34  includes a through opening  42 , which receives an end of lifter rod  20 . An opposite end of through opening  42  is enlarged at  44  to receive an enlarged gripping portion  45  of an adjustment screw  46 . Adjustment screw  46  includes a through opening  48  to receive a fastener  50 , which passes through the adjustment screw and into a threaded end of lifter rod  20 . An external surface  52  of adjustment screw  46  is threaded to mate with an internally threaded surface of through opening  42 . This allows adjustment screw  46  to be threadably adjustable with respect to rod carrier  34 . This allows the rod carrier relationship to the lifter foot assembly to be adjusted by manipulation of gripping portion  45 , such as with a wrench. A setscrew  54  positioned in an opening  56  in rod carrier  34  captures the adjustment screw  46  to prevent it from being removed from the rod carrier. A pair of end plates  58  retains the appropriate spacing of the gib plates and captures the carrier assembly in camming surfaces  32  to prevent separation therefrom. Mounting openings  60 , which extend the full height of the respective gib plates, provide for mounting of the lifter foot assembly to the ejector plate. 
   In operation, helper pin  26  is fixed to ejector block  12  and clamp plate  14  at the same angle as lifter rod  20 . Because rod carrier  34  and helper carrier  36  are pivotally mounted with respect to the gib plates, lifter foot assembly  22  may be utilized with various angular orientations of the lifter rod and helper pin. In the illustrative embodiment, the lifter rod and helper pin may be positioned at an angle of 0 to 15 degrees with respect to the direction of movement of the ejector plate and may even be utilized at an angle of up to approximately 20 degrees with respect to the direction of movement of the ejector plate. As the ejector plate actuates lifter rod  20  upwardly, helper carrier  36  slides along helper pin  26 . Also, as the ejector plate  16  moves, the carrier assembly  30  moves laterally. This is assisted by the helper pin which assists in causing the slidable motion of the carrier assembly thereby reducing the lateral force placed upon the lifter rod. 
   In operation, helper pin  26  is fixed to ejector block  12  and clamp plate  14  at the same angle as lifter rod  20 . Because rod carrier  34  and helper carrier  36  are pivotally mounted with respect to the gib plates, lifter foot assembly  22  may be utilized with various angular orientations of the lifter rod and helper pin. In the illustrative embodiment, the lifter rod and helper pin may be positioned at an angle of 0 to 15 degrees with respect to the direction of movement of the ejector plate and may even be utilized at an angle of up to approximately 20 degrees with respect to the direction of movement of the ejector plate. As the ejector plate actuates lifter rod  20  upwardly, helper carrier  36  slides along helper pin  26 . Also, as the ejector plate  16  moves, the carrier assembly  30  moves laterally. This is assisted by the helper pin which assists in causing the slidable motion of the carrier assembly thereby reducing the lateral force placed upon the lifter rod. 
   Referring now to the illustration in  FIGS. 8   a–   8   d,  upon completion of the molding operation, the ejector plate is spaced apart from the ejector block, as illustrated in  FIG. 8   a.  The ejector plate begins moving away from the clamp plate and toward the ejector plate, as illustrated in  FIG. 8   d,  in the direction of ejector plate travel. This places a force on the carrier assembly which would, otherwise, cause a force F to be placed on the carrier rod and lifter foot assembly without the presence of the helper carrier. As illustrated in  FIG. 8   c,  the ejector plate continues to move in the direction of the ejector block, thereby ejecting the part with lift body  18 . The ejection is complete in  FIG. 8   d.  The ejector plate then returns to its initial position, as illustrated in  FIGS. 8   a  and  8   b.    
   Thus, it is seen that the present invention provides a universal lifter foot assembly that is exceptionally versatile and allows the mold designer to utilize common components without the necessity for detailed design of the elements thereof. Moreover, a carrier assembly and gib plates may be kept in stock with the angle of the camming surfaces either machined at the time of use or stocked at various angles of inclination. Other modifications will become apparent to those skilled in the art. 
   Thus, it is seen that the present invention provides a universal lifter foot assembly that is exceptionally versatile and allows the mold designer to utilize common components without the necessity for detailed design of the elements thereof. Moreover, a carrier assembly and gib plates may be kept in stock with the angle of the camming surfaces either machined at the time of use or stocked at various angles of inclination. Other modifications will become apparent to those skilled in the art. 
   Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.