Abstract:
A mold assembly, a method of molding, and a molded component for an interior of a vehicle using two shots of material. The mold assembly includes first and second mold halves cooperating to define a cavity. One of the mold halves includes a retractable core. The second mold half defines a divider for engaging the retractable core, when the retractable core is extended, so as to divide the mold cavity into first and second chambers. Portions of the core cooperate to define a sloped surface on the first shot that aids in inhibiting flash forming as the second shot is introduced into the mold assembly.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to a mold assembly and method for molding a two-shot component for use as a trim assembly in a passenger compartment of a motor vehicle.  
         [0003]     2. Related Technology  
         [0004]     Vehicle interiors, such as door panels, instrument panels, and the like often include a component made of a thermoplastic material. Occasionally, for aesthetic purposes, it is desirable for the component, or more specifically for a portion of the component that is exposed to the vehicle occupants (commonly known as the “A” or “show” surface have two or more differently-colored sections. Additionally, or alternatively, it may be desirable for the component to have two or more sections with different textures or patterns so that the component has a bi-textured feel.  
         [0005]     One current way at achieving a bi-colored component includes painting a first area a first color and painting a second area another color. In an alternative construction, only the first area is painted and the remaining area remains its natural color. Another construction for a bi-colored component includes manufacturing a component through a powder slush process. More specifically, a portion of a mold inner surface is coated with a powder having a first color and the remaining portion of the mold inner surface is coated with a powder having a second color. The mold is then heated, sintering the first and second powders and bond them together to form the component.  
         [0006]     The above constructions, however, may result in an undesirably irregular or non-continuous border between the differently colored areas. Moreover, painted areas of the show surface may be more prone (than non-painted areas) to premature color fading and/or paint chipping or cracking. Furthermore, it may not be possible to produce a component having a bi-textured skin through painting alone.  
         [0007]     Yet another known bi-colored construction uses a two-shot molding process. A first shot of molten material is injected into a first chamber to form a first skin component and a second shot of molten material is injected into a second chamber to form a second skin component. This can occur in a single mold, if a retracting core is slidably positioned within the mold assembly for selectively separating and connecting the respective chambers. For Example, the first shot is delivered to the mold when the retractable core is in a closed position. As a result, the material is only able to flow into a first chamber of the mold cavity. Upon retraction of the core into an open position, a second shot of material is able to flow throughout the remainder of the mold cavity.  
         [0008]     One limitation of the above is that, when the core is retracted, the first shot of material is no longer restrained against the mold surface and may be susceptible to flashing. More specifically, flashing occurs when the first shot is able to move away from the mold and the second shot flows between the first shot and the mold surface, thereby contaminating the show surface of the component with extra, undesirable material and/or misaligning the respective portions of the component with respect to each other.  
         [0009]     Obviously, it would be advantageous to provide a component having a structure that resists flashing and to provide a mold assembly and method that substantially reduce flashing.  
       SUMMARY  
       [0010]     In overcoming the limitations and drawbacks of the prior art, the present invention provides a mold assembly for assembling a component, a method for assembling a component, and a component for an interior of a vehicle.  
         [0011]     In one aspect of the present invention, a mold assembly includes a first mold half having a receiving slot, a second mold half cooperating with the first mold half to define a mold cavity, and a retractable core positioned within the receiving slot so as to be slidable between a retracted position and an extended position. The second mold half defines a divider extending towards the receiving slot and engaging the retractable core when the retractable core is in the extended position so as to divide the mold cavity into first and second chambers. The divider therefore reduces flashing by acting as a shield for the leading edge of the first shot of material.  
         [0012]     The retractable core includes an engagement surface that engages the divider when the retractable core is in the extended position. The retractable core also preferably defines a sloped portion sloping away from the engagement surface along a first axis and away from the second mold half along a second axis perpendicular to the first axis. The sloped portion therefore further reduces flashing by diverting the flow of the second shot of material towards the second cavity and urging the first shot of material into tight engagement with the mold surface. The sloped portion may be any suitable shape, such as linear or arcuate.  
         [0013]     In another aspect of the present invention, a method of assembling a component for an interior of a vehicle includes the steps of positioning a retractable core in an extended position so as to engage a divider portion and divide a mold cavity into first and second chambers, injecting a first shot of material into the chamber so that the leading edge of the first shot engages the divider, moving the retractable core to a retracted position, and injecting a second shot of material into the second chamber so that the material flows between the first shot and the retractable core. The step of injecting the second shot of material preferably occurs before the first shot of material is fully hardened so as to reduce cycle time and improve bonding between the respective shots.  
         [0014]     In yet another aspect of the present invention, a component for a motor vehicle interior includes a first skin portion and a second skin portion engaging each other. The first skin portion includes an A-surface and a B-surface intersecting along a first skin leading edge and cooperating to define a generally sloped portion. The first and second skin portions cooperate to define a show surface exposed to the motor vehicle interior and to define an indentation extending along the first skin leading edge.  
         [0015]     Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a cross-sectional view of an injection molding assembly for molding a motor vehicle interior component and embodying the principles of the present invention;  
         [0017]      FIG. 2  is an enlarged view of the injection molding assembly taken along line  2 - 2  in  FIG. 1  having upper and lower molds defining a mold cavity and a retractable core disposed within a slot of the lower mold;  
         [0018]      FIG. 3  is an enlarged view of the injection molding assembly seen in  FIG. 2 , where a first chamber of the mold cavity has been filled with a first shot of material;  
         [0019]      FIG. 4  is an enlarged view of the injection molding assembly seen in  FIG. 3 , where the core has been moved to a retracted position;  
         [0020]      FIG. 5  is an enlarged view of the injection molding assembly seen in  FIG. 4 , where a second chamber of the mold cavity is partially filled with a second shot of material;  
         [0021]      FIG. 6  is an enlarged view of the injection molding assembly seen in  FIG. 5 , where the second chamber of the mold cavity is completely filled with the second shot of material;  
         [0022]      FIG. 7  is an enlarged cross-sectional view of an alternative embodiment of an injection molding assembly for molding a motor vehicle interior component embodying the principles of the present invention; and  
         [0023]      FIG. 8  is an enlarged cross-sectional view of another embodiment of an injection molding assembly for molding a motor vehicle interior component and embodying the principles of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0024]     Referring now to the drawings,  FIG. 1  shows an injection mold assembly  10  for molding a component  12  ( FIG. 6 ) for the interior of a motor vehicle. The molding assembly  10  generally includes a lower mold  14 , an upper mold  16 , a retractable core  18  disposed within a slot  20  of the lower mold  14 , and a pair of injection assemblies  22 ,  24  for delivering molten material. The molds  14 ,  16  cooperate to define a mold cavity  26  and the upper mold cooperates with the retractable core  18  to divide the cavity  26  into a first chamber  28  and a second chamber  30 . More specifically, the retractable core  18  is slidable within the slot  20  between an extended position  34  ( FIGS. 1, 2  and  3 ) and an open position  36  ( FIGS. 4, 5  and  6 ). When the retractable core  18  is in the extended or closed position  34 , an engagement surface  38  engages a divider  32  formed on the mold surface of the upper mold  16  and extending towards the slot  20 . With this contact, the core  18  divides the cavity  26  into the first and second chambers  28 ,  30 .  
         [0025]     Referring to  FIG. 2 , the retractable core  18  is shown in more detail and includes the engagement surface  38 , for contacting the divider  32 , and a sloped portion  40 , for causing the molten material to flow as desired. The sloped surface  40  slopes from the contact surface  38  in a direction away from the upper mold  16 . As will be more fully discussed below, this surface  40  defines a design line configuration on a first shot of material injected into the first mold cavity  28 . This sloped design line configuration promotes pressure on the back of the first shot during the second shot of material, effectively sealing the first shot against the mold  16  to inhibit the formation of flash along the design line. In other words, the sloped portion  40  generally defines a negative slope measured along the axes  42 ,  44  shown in  FIG. 2  for reducing flashing.  
         [0026]     As a result of its height, the divider  32  is able to substantially shield the molten material at the first shot located in the first chamber  28  and also aid in reducing flashing.  
         [0027]     As shown in  FIGS. 1 &amp; 3 , the first injection assembly  22  delivers a first shot  50  of molten material through a first injection port or conduit  52  and into the first chamber  28  of the cavity  26 . The first shot general trails along a first shot path in the direction of arrow  54 . More specifically, with the core  18  closed, the first shot  50  preferably completely fills the first chamber  28  so that the first shot  50  engages the divider  32 .  
         [0028]     The first shot  50  of molten material defines a first skin component  58  of the component  12 . The first skin component  58  may be made of any suitable material, such as thermoplastic. Because it is typically visible from the vehicle interior, the first skin component  58  is preferably formed from a molten material having a desirable color so that painting and/or dyeing is unnecessary.  
         [0029]     After the first shot  50  of molten material fills the first chamber  28  and has sufficiently cooled so as to retain its shape, the core  18  is retracted to its retracted or open position  36 , as seen in  FIG. 4 . The retractable core  18  is preferably able to be retracted without opening the mold assembly  10 . The construction of retractable cores is generally well known and, therefore, further detailed description is not provided herein  
         [0030]     Although the retractable core  18  may be retracted to the open position  36  any time after the first shot  50  is delivered to the first chamber  28  and the first shot has cooled so as to be able to retain its shape, the retraction preferably occurs when the first shot  50  has not yet fully hardened. More specifically, the retractable core  18  is preferably retracted 10 seconds or less after the first chamber  28  has been completely filled with molten material. By retracting the core  18  shortly after the first shot  50  is delivered, the overall cycle time for the resulting component can be reduced, thereby increasing productivity and lowering manufacturing costs. Furthermore, undesirable gaps or imperfections in that portion of the component  12  defined by the first shot  50  are reduced by a relatively quick retraction of the core  18  and delivery of the second shot. More specifically, molten material shrinks as it cools and thereby can create gaps between the molding and the molds  14 ,  16 . These gaps may promote flashing and or part misalignment during later stages of the molding process, as will be discussed further below.  
         [0031]     As the retractable core  18  moves into the retracted position  36 , the second chamber  30  is enlarged and a B-surface  60  of the first shot  50  partially defines the enlarged second chamber. As used herein, the term “B-surface” refers to a surface that is not exposed in the vehicle&#39;s interior during normal use of the vehicle. A portion of the B-surface  60  corresponding to the surface  40  of the core  18  now defines a ramped surface  61  adjacent to the design line or edge  63  of portion of the component defined by the first shot  50 . This ramped surface  61  generally extends from the end of the design line  63  in such a direction that the thickness of the first shot  50  generally increases to the nominal thickness of the component.  
         [0032]     Next, the second injection assembly  24  delivers a second shot  62  of molten material through a second injection port or conduit  64  into the enlarged second chamber  30  of the cavity  26 . The second shot  62  flows along a second shot path as generally indicated by arrow  66 . As the second shot  62  fills the second chamber  30 , a leading edge  68  of the second shot  62  flows past the divider  32 , between the first shot  50  and the retractable core  18  the divider  32  and encounters the transition surface  61  of the first shot  50 . As a result of the sloped shape of this surface  61 , the design line  63  and the first shot  50  are forced or pressed into the upper mold  14  by the pressure exerted by the second shot  62 . The second shot  62  continues until the enlarged second chamber  30  is completely filled and the leading edge  68  of the second shot  62  engages a side wall  69  of the slot  20 .  
         [0033]     Upon filling of the enlarged second chamber  30 , the molding process enters what is referred to as the “pack and hold” phase of the molding cycle. During this phase, pressure is applied via the second slot  62  forcing both shots against the cavity side or A-surface side of the upper mold  16 . The pressure exerted by the second shot  62  effectively seals the design line  63  against the first shot  50  against the upper mold  16  and will not allow the second shot  62  to flash to the A-surface side of the first shot  50 , thus ensuring a crisp, flash-free design line  63  in the resulting component.  
         [0034]     The second shot  62  of molten material defines a second skin portion  70  of the component  12 . The second skin portion  70  may be made of any suitable material, such as thermoplastic. Because it is typically visible from the vehicle interior, the second skin portion  70  is preferably formed from a molten material having a desirable color so that painting and/or dyeing is unnecessary. It may be desirable for the colors of the respective skin portions  58 ,  70  to be different so that the component  12  has a two-tone appearance.  
         [0035]     As seen in the figures, the divider  32  extends a distance substantially equal to the thickness of the first shot  50 . As a result of its height, the divider  32  is able to substantially shield design line  63  of the first shot  50  from the second shot  62  of material and reduce flashing. More specifically, the divider  32  diverts the flow of the second shot  62  around the first shot  50  and onto the sloped surface  61 , which presses the first shot  50  into the upper mold  16 . Therefore, the diverted second shot  62  of material is more likely to flow into the enlarged second chamber  30  than to flash between the first shot  50  and the upper mold  16 .  
         [0036]     Also as a result of the height of the divider  32 , the second shot  62  is formed so its A-surface has about the same “perceived” height as the A-surface of the first shot  50 . The divider  32  therefore defines the joint or line between the two skin portions along the A-surface of the final component.  
         [0037]     To maximize the beneficial forcing of the first shot  50  into the cavity surfaces of the upper mold  16 , the angle of the transition surface  61  is shallow and preferably defines an angle with respect to a horizontal axis  42  (or generally the A-surface of the first shot  50 ) that is less than or equal to 45 degrees. Even more preferably the angle is about 25 degrees or less.  
         [0038]     After the enlarged second chamber  30  is completely filled by the second shot  62 , the first and second skin portions  58 ,  70  are allowed to cool, the mold is opened, and the component  12  is removed. The skin portions  58 ,  70  are preferably allowed to cool for a time period longer than the duration between the first and second shots so that the resultant component  12  is substantially hardened before removal. More specifically, the component  12  is preferably allowed to harden for 30 or more seconds before removal from the mold assembly  10 .  
         [0039]     As shown in  FIG. 6 , the first skin portion  58  defines an A-surface intersecting with the A-surface of the second skin portion  70 . The first and second skin portions  58 ,  70  thus cooperate to define a show surface  77  exposed to the vehicle interior.  
         [0040]     Referring now to  FIG. 7 , an alternative embodiment of the present invention is shown. This embodiment differs from the prior embodiment in that the mold assembly  110  has a retractable core  118  with a generally arcuate sloped portion  140  instead of a flat portion  40 . As a result, the first skin portion  158  includes a generally arcuate sloped portion  141  so that the second shot  162  of material urges the first skin portion  158  toward the upper mold  116 .  
         [0041]     Referring now to  FIG. 8 , another alternative embodiment of the present invention is shown. In this embodiment, the mold assembly  210  has a retractable core  218  with a generally flat portion  282  and an upwardly (toward the upper mold  216 ) sloping portion  284 . As a result, the first shot  250  includes a corresponding flat portion  283  and an upwardly sloped portion  285 . This configuration causes the second shot  262  of material to flow along a horizontal axis  42  or flow path with minimal reaction forces when passing the flat portion  283  and to flow upwards (relative to the vertical axis  44 ) when passing the sloped portion  285 . This urges orientation of the first shot  250  upwards and to the left (in  FIG. 8 ), further promoting engagement between the first shot  250  and the upper mold  216 .  
         [0042]     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.