Abstract:
An undercut release component having an end configured for molding a part having an undercut is disclosed wherein the configured end disengages from the molded undercut by traveling in a 3-axis path. A process for providing undercut release in a mold is also disclosed.

Description:
BACKGROUND OF INVENTION 
     The present invention is directed to the field of mold design. More particularly, the present invention is directed for providing undercut release for molding parts having undercuts. Internal core lifters are used within a mold device to mold and eject undercuts in injection molds. An internal core lifter generally consists of a core blade seated at a predetermined angle achieved by mounting one end of the core blade at a fixed angle to a coupling which then slides linearly along a support mounted to the mold ejection plates. 
     In order to mold undercuts and eject the parts, the core lifter has a core blade that is attached to one ejector system of the mold, and the opposite end of the core blade is used to mold and eject the part. To mold undercuts, the core blade is placed at an angle determined by the mold design. Since one end of the core blade is configured to mold the undercut of the plastic part, the core blade is required to move horizontally away from the undercut during a vertical ejection of the part. This horizontal movement is necessary during ejection so as not to damage the part. 
     In a typical prior art undercut release system, an ejector blade is engaged with the mold. The ejector blade travels through a slide or slot in the mold. One end of the ejector is configured to provide the undercut of the molded part when the ejector blade is aligned with the internal mold cavity of the mold. The opposite end of the ejector blade is attached via a coupling to an ejector plate. The coupling is designed to transmit pushing and pulling forces to the ejector blade. The coupling is also designed to allow the ejector blade to travel in a linear direction to provide clearance for the formed undercut of the part. The movement of the ejector blade forward provides clearance from the undercut and the movement of the ejector blade upward helps eject the part from the mold cavity. A representative example of such a prior art undercut release system is disclosed in U.S. Pat. No. 5,137,442. 
     Previous undercut release apparatuses have relied on planar motion of the core lifters to provide release from the molded undercut. However, due to the part configuration, it may be desirable or necessary for the release mechanism to travel off plane in order to avoid damaging the molded part. Such off plane, or three-axis, movement is a hallmark of the present invention. 
     SUMMARY OF INVENTION 
     In one embodiment, the invention comprises an apparatus for molding parts having at least one undercut, the apparatus comprising: (i) an undercut release component having a body with a first end configured for molding a part having an undercut wherein the undercut release component is capable of movement whereby the first end moves away from the undercut in a 3-axis path. 
     In another embodiment, the invention comprises an undercut release component comprising: (i) a body having a first end configured for molding a part having an undercut and an opposite second end adapted for transmitting and receiving both pushing and pulling forces, wherein the undercut release component is slideably engaged with an injection. mold assembly; and, (ii) a coupling engaged with the second end for transmitting pushing and pulling forces to the second end and allowing nonlinear movement of the second end, wherein the undercut release component is capable of movement whereby the first end moves away from the undercut in a 3-axis path. 
     In-another embodiment, the invention comprises a process for providing undercut release in a mold, the process comprising the steps of: (i) providing an undercut release component having a first end, the first end configured for molding a part having an undercut, the undercut release component being movably engaged with the mold; and (ii) moving the undercut release component alternately between a first position wherein the first end aligns with the mold to form a continuous molding surface and a second position wherein the first end is disposed away from the undercut, wherein the first end traces a 3-axis. path when moving between the first position and the second position. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the following accompanying drawings, which are for illustrative purposes only. Throughout the following views, reference numerals will be used in the drawings, and the same reference numerals will be used throughout the several views and in the description to indicate same or like parts. 
     FIG. 1 is a side view of a mold apparatus incorporating the present invention. 
     FIG. 2 is a side view of the mold apparatus of FIG. 1 with the undercut release components in an open position. 
     FIG. 3 is a side view of the mold apparatus of FIG. 2 with the molded part fully disengaged from the undercut release components. 
     FIG. 4 is a top view of the mold apparatus of FIG. 1 taken along line  4 — 4  of FIG.  1 . 
     FIG. 5 is a top view of a section of the mold apparatus of FIG. 4 showing the undercut release components in an engaged position. 
     FIG. 6 is a top view of a section of the mold apparatus of FIG. 4 showing the undercut release components in an open position. 
     FIG. 7 is a cross-sectional view of the mold apparatus taken along line  7 — 7  of FIG.  5 . 
     FIG. 8 is a cross-sectional view of the mold apparatus taken along line  8 — 8  of FIG.  6 . 
     FIG. 9 is a cross-sectional view of the mold apparatus taken along line  9 — 9  of FIG.  8 . 
     FIG. 10 is a front view of an undercut release component. 
     FIG. 11 is a side view of the undercut release component of FIG.  10 . 
     FIG. 12 is a top view of the undercut release component of FIG.  10 . 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, references made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the spirit and scope of the present invention. 
     In one preferred embodiment, the present invention comprises an undercut release system comprising an undercut release component engaged with a mold. One end of the undercut release component is configured to form the undercut of the molded part. The opposite end of the undercut release component is adapted to receive and transmit pushing and pulling forces from the ejector plate. The body of the undercut release component comprises a twist. The twist represents a segment of a helix. The helix is defined by its mathematical terms, i.e., a three-dimensional curve that lies on a cylinder or cone, such that the curve&#39;s angle to a plane perpendicular to the cylinder or cone axis is constant. Typically, the radius of the cylindrical helix is the same as the radial distance of the undercut release component within the mold cavity. The angle of the twist curve, or helix, is determined by the desired angle of traverse for the undercut release compound through the mold assembly. The slot or channel within the mold assembly which receives the undercut release component is also configured with a helical shape corresponding to the helical shape of the undercut release component in the mold. Movement of the ejector plate towards and away from the mold causes the undercut release component to move back and forth within the mold slot. This back and forth movement causes the configured end of the undercut release component to move upward, forward and along a helical path. Such movement is known herein as 3-axis or non-planar movement. This 3-axis movement of the undercut release component provides clearance from the undercut and aids in ejecting the part from the mold cavity. The 3-axis motion allows the undercut release component to clear portions of the molded part lying inline with the molded undercut. The coupled end of the undercut release component also travels a corresponding three-axis path. As such, the coupling means must accommodate nonlinear movement within the coupling. Such nonlinear coupling may be accomplished by providing a pivot ball mounted to the coupling end of the undercut release component. The pivot ball is received and contained within an arcuate channel within the ejector plate. The arcuate channel allows the pivot ball to move forward and back along the curved channel in a nonlinear direction. 
     The invention is illustrated in the following preferred embodiment. 
     FIG. 1 shows a mold apparatus  20  comprising an embodiment of the present invention. The mold apparatus  20  comprises lower mold plate assembly  22 , upper mold plate assembly  24  and first ejector plate  26 . Upper mold plate assembly  24  is shown in the open position. First ejector plate  26  is shown in the closed or engaged position. Undercut release component  28  is slideably engaged with lower mold plate assembly  22  and is coupled with first ejector plate  26 . Undercut release component  28  has a first configured end  30  which is adapted to engage with the mold assemblies to form the undercut in a molded part. Undercut release component  28  has a second coupled end  32  which engages with first ejector plate  26 . In a preferred embodiment of the coupling, coupling pivot ball  34  attached to coupled end  32  is contained within coupling channel  36  of first ejector plate  26 . Preferably, the mold apparatus  20  also comprises an ejector  38  coupled to second ejector plate  44 . Ejector  38  aids in the removal of molded part  40  from the mold apparatus  20 . 
     FIG. 2 shows mold apparatus  20  at an intermediate stage of ejection of molded part  40 . First ejector plate  26  and second ejector plate  44  have advanced towards lower mold plate assembly  22 . As a result of the advancement of first ejector plate  26  and second ejector plate  44 , undercut release components  28  and ejector  38  have moved molded part  40  away from the mold cavity on lower mold plate assembly  22 . Additionally, the movement of undercut release component  28  has disengaged configured end  30  from the molded undercut  42  on molded part  40 . In disengaging from the molded undercut  42 , configured end  30  travels in a 3-axis path as described in detail below. 
     FIG. 3 shows mold apparatus  20  at the end of the ejection cycle. Second ejector plate  44  has advanced further towards lower mold plate assembly  22  then as shown in FIG.  2 . The further advancement of second ejector plate  44  provides for further movement of ejector  38  thereby providing complete disengagement of molded part  40  from the mold on lower mold plate assembly  22  and from undercut release components  28 . 
     FIG. 4 shows a top view of lower mold plate assembly  22  which comprises part of lower mold plate assembly  22  as shown along line  4 — 4  of FIG. 1. A number of undercut release components  28  are shown arranged along a mold surface circumference  48 . As shown, undercut release components  28  are configured so that configured ends  30  provide a continuous molding surface along mold surface circumference  48  and also a form and undercut. Undercut release components  28  are shown in the engaged or closed position. 
     FIGS. 5 and 6 show sectional views of lower mold plate assembly  22 . FIG. 5 shows the sectional view with undercut release component  28  in the closed or engaged position such that configured end  30  is continuous with mold surface circumference  48 . FIG. 6 shows undercut release component  28  in the open or ejection position. In FIG. 6, configured end  30  has advanced above the surface of lower mold plate assembly  22  along a path that moves upward towards the viewer forward to the viewer&#39;s left and nonlinearly along the circumference of mold surface circumference  48 . The position change of configured end  30  between FIG.  5  and FIG. 6 illustrates the nonlinear aspect of the 3-axis movement of the present invention. The forward and upward movement of configured end  30  is further illustrated in FIGS. 7-9. 
     FIG. 7 shows a cross-sectional side view taken along line  7 - 7  of FIG.  5 . Undercut release component  28  engages with lower mold plate assembly  22  via mold assembly slot  50 . Undercut release component  28  traverses support plate  52  through support plate relief  54 . Likewise, undercut release component  28  traverses second ejector plate  44  though second ejector plate relief  56 . Coupling pivot ball  34  connected to coupling end  32  resides in coupling channel  36  of first ejector plate  26 . Coupling pivot ball  34  extends through coupling channel slot  58 . Both coupling channel  36  and coupling channel slot  58  are nonlinear, typically arcuate. In the closed or engaged position shown in FIG. 7, pivot ball  34  is positioned towards the viewer&#39;s right along coupling channel slot  58 . 
     FIG. 8 shows the cross-sectional view taken along line  8 — 8  of FIG.  6 . In this view, the undercut release component  28  is in the open or ejected position. Undercut release component  28  has advanced through mold assembly slot  50  thereby moving configured end  30  upwards above lower mold plate assembly  22  and forward to the viewer&#39;s left in relation to mold assembly slot  50 . Likewise, coupling pivot ball  34  has advanced forward to the viewer&#39;s left along coupling channel  36  and coupling channel slot  58 . 
     FIG. 9 shows a cross-sectional view along line  9 — 9  of FIG.  8 . FIG. 9 provides another view of the coupling of coupling pivot ball  34  with coupling channel  36  and coupling channel slot  58 . 
     FIGS. 10-12 are front, side and top views of a typical undercut release component  28  of the current invention. The views of FIGS. 10-12 illustrate the twist in the body of undercut release component  28 . 
     In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.