Abstract:
Method for insert molding film covered plastic parts are disclosed that facilitate wrapping of the paint film around edges of the part. A mold cavity ( 210 ) is provided wherein the requisite edge extremities ( 212, 214 ) of the cavity ( 210 ) are provided in an offset or spaced relation to the mold parting line plane ( 216 ). Location of the mold extremities at this position helps to secure the paint film in the mold cavity ( 210 ) and prevents pinching of the film that would otherwise occur along the mold parting line ( 216 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Priority filing benefit of (1) International PCT application PCT/US01/17547 filed May 31, 2001, and published under PCT 21(2) in the English language and (2) U.S. provisional application Ser. No. 60/211,040 filed Jun. 12, 2000. 
   FIELD OF THE INVENTION 
   The present invention pertains to improved methods of insert molding a laminated film or the like over a plastic substrate and to the fused film—plastic parts made thereby. 
   BACKGROUND OF THE INVENTION 
   A variety of injection molded parts have been made and used for motor vehicle body and trim parts. For example, bumpers, body panels, doors, filler panels, wheel covers, dashboards, arm rests and other parts have been made via injection molding techniques. Additionally, with regard to vehicle exteriors, bodyside moldings, beltline moldings, roof moldings, window moldings, chin spoilers, and rocker panels, etc. are made via injection molding of PVC or other thermoplastic materials. 
   In order to provide a painted surface for these parts, film lamination techniques have been successfully employed. In accordance with these processes, a paint film laminate is insert molded with the desired thermoplastic to fuse the film over the injection molded part. The resulting injection molded part is ready for assembly without subsequent painting. 
   The paint film laminate used in these insert molding techniques may comprise a backing sheet of about 0.020″ in thickness to which paint layers are adhered. Typically, the backing sheet comprises an extruded thermoplastic sheet. 
   In such paint film laminates, a paint film comprising a cast dried continuous paint coating, is provided over the backing sheet. The paint film may consist of a monocoat, a clear coat over a base coat, or a clear coat and a base coat with interposed print or design. The paint film, including base coat, clear coat and print or design, if desired, may range from about 0.5-4 mil. in thickness. 
   The laminated paint films are available, for example, from a variety of manufacturers. The films are typically provided in a roll, unwound and then trimmed to a proper “preformed” size and shape, ready for insertion into the injection mold. The preform is usually placed along the cavity side of the mold with the painted side thereof facing the mold cavity surface. In some instances, the preform may be placed along the core side of the mold. The mold is then clamped and the desired molten resin is injected into the mold cavity. Heat and pressure conditions in the mold partially melt the backing sheet and a melt bonding or fusion of the injected resin and film occur. Injection molds used for these processes are rear or edge gated so that the molten resin is directed along the backside of the film. 
   Although these processes provide significant advantage, they are not without problem. For example, edge portions of the part, such as the longitudinally extending edges of elongated strips used for body moldings and the like, may not be completely covered with the film. Accordingly, these edges reveal the uncovered plastic substrate and provide an aesthetically displeasing appearance since the continuity of the printed surface is interrupted by the unsightly appearance of the underlying plastic substrate. 
   A variety of methods have been developed to cover the edge portions of these co-molded strips. For example, in accordance with U.S. Pat. Nos. 5,599,608 and 5,783,287 (both of common assignment herewith), the paint film is pre-formed prior to the co-molding step so that the longitudinally extending edge portions thereof have re-entrant dispositions relative to the remaining body of the film. Additionally, as set forth in U.S. Pat. No. 5,746,962 (of common assignment herewith), edgewise extremities of the mold cavity, referred to as “pockets,” are provided contiguous to the mold parting line so that, upon co-molding, the desired end of the film positioned in the pocket will be superposed over the molten plastic injected into the pocket. This forms an edge portion of the resulting plastic part wherein the film substantially covers the edge. 
   The technology reported in the above patents has proven tremendously successful, especially in connection with the manufacture of deep draw or deep dimension parts. However, in the manufacture of relatively flatter trim parts, product reject problems have been encountered due to shifting or rotation of the film in the mold cavity prior to injection of the molten plastic. Additionally, high pressure pinching of the film between the male and female mold platens along the mold parting line also results in undesirable product rejects. 
   With respect to this latter problem, the high pinching force (usually on the order of about 600 tons) can result in a serrated or feathered edge appearance of the film laminate along the edge of the plastic part thereby leading to the requirement of an additional labor-intensive product trimming step so that the product can comply with stringent product quality standards. 
   SUMMARY OF THE INVENTION 
   Briefly, improvement in prior art techniques is provided by utilization of a specific mold cavity structure which facilitates wrapping of the paint film around the desired edge portion of the plastic part while minimizing the chance that the film will shift or rotate out of proper alignment in the mold cavity. Additionally, the cavity structure provides for a distinct physical separation of the edge extremity of the mold cavity from the mold parting line. This feature helps to minimize high pressure pinching of the film edge that may otherwise occur in the high pressure nip location existing at the mold parting line. 
   More specifically, the mold comprises a male, core portion and a female concavity portion. Together, the space between the core portion surface and concavity surfaces defines a mold cavity adapted for receipt of a paint film laminate therein normally positioned with its show surface facing the concavity. As per conventional practice, the sprue and gating are attached to the core side of the mold. Of course, the relative positioning of the film in the mold cavity and the direction of the plastic entry and flow into the mold cavity could be easily switched. 
   A mold parting line is defined by the mating surfaces of the male and female mold portions. An extremity of the mold cavity is provided in one of the mold surfaces, typically in the core portion. This extremity upon completion of molding, will form an edge of the desired plastic part. This extremity is referred to herein as a wrap around surface. 
   In contrast to prior art structures and methods in which the mold extremity is located along or is contiguous with the parting line of the mold, the wrap around surface in accordance with the invention is offset or spaced from the mold parting line as measured along a vector perpendicularly oriented with respect to the plane defined by the mold parting line. 
   Molten plastic is inserted into the mold cavity and is directed against the wrap around surface and the paint film end positioned at this extremity of the mold cavity. The paint film end will pivot along the wrap around surface to thereby form the desired plastic part wherein an edge portion of the plastic will be substantially covered or wrapped by overlying paint film. 
   The invention will be further described in conjunction with the appended drawings and following detailed description. 

   
     DRAWINGS 
       FIG. 1  is a sectional view of a prior art mold cavity; 
       FIG. 2  is a magnified sectional view of a portion of the prior art mold cavity shown in  FIG. 1 ; 
       FIG. 3  is a sectional view of a preferred mold cavity in accordance with the invention; 
       FIG. 4  is a magnified sectional view of a portion of the mold cavity shown in  FIG. 3  shown with a co-molded paint film laminate and underlying plastic material therein; 
       FIG. 4   a  is a magnified sectional view of a mold cavity in accordance with another embodiment of the invention; 
       FIG. 5  is a magnified sectional view of a portion of a paint film laminate covered plastic trim part made in accordance with the invention; 
       FIG. 6  is a plan view of a paint film covered plastic trim part made in accordance with the invention; and 
       FIG. 7  is a transverse cross sectional view of the trim part shown in  FIG. 6 , taken along the lines and arrows  7 - 7  of  FIG. 6 . 
   

   DETAILED DESCRIPTION 
   Turning first to  FIGS. 6 and 7  of the Application, there is shown a trim part such as a bodyside molding member  6  made in accordance with the invention. The trim part  6  is elongated and presents an aesthetically pleasing appearance due to the provision of the show side  8  of paint film laminate over the plastic substrate  10 . 
   As can be best seen in  FIG. 7 , the longitudinally extending edges  12 ,  14  of the substrate  10  are completely covered or wrapped around at wrapped edges  18 ,  20 , by the paint film  16 . The part shown in  FIGS. 6 and 7  is provided in accordance with the instant co-molding process as shall be set forth hereinafter. 
   Turning now to  FIG. 1  of the invention, there is shown a prior art mold of the type utilized to produce plastic parts. Here, the mold  100  comprises a male core member  102  and cooperating female member  104 . The male mold member comprises a convex core surface  106  which cooperates with the female concave surface  108  to, therebetween, define a mold cavity  110  in which the paint film covered parts are made. 
   The longitudinal extending edge extremities of the mold cavity are provided as a pair of surfaces which will extend longitudinally along the finished, molded elongated part. Here, left hand extremity  112  and right hand extremity  114  are provided. Note that both of these extremities are contiguous with the horizontally disposed part line of the mold shown at  116 . 
   With further regard to  FIG. 1 , sprue  118  is in communication with a source of molten plastic so that it may serve as an entry location for plastic flow into the mold cavity. 
   The step of co-molding itself is not new. In accordance with traditional co-molding techniques, the paint film laminate is first placed in the mold cavity, typically with the show side of the paint film laminate contiguous to or spaced closely from the concave surface  108  presented by the female portion of the mold. Then, plastic is injected through the sprue, and fills the mold so that the resulting co-molded part consists of a plastic substrate covered by paint film laminate along the face and edges of the substrate. 
   As shown in  FIG. 2 , the right hand extremity  114  of the prior art mold cavity is contiguous with the parting line of the mold  116 , in accordance with prior art processes and structures. 
     FIG. 3  of the drawings depicts a mold cavity made in accordance with the invention. Here, the mold  200  comprises core member  202  and cooperating female member  204 . The male core surface is shown at  206  with the cooperating surface of the female mold member shown at  208 . Between the members  206  and  208 , a mold cavity  210  in accordance with the invention is provided. Here, the left hand and right hand edge extremities of the mold cavity  212 ,  214  respectively, are off set from the part line  216  of the mold. That is, the edge extremities  212 ,  214  are spaced from the part line  216  as would be measured along a vector positioned perpendicular to the part line  216 . Instead, the edge extremities  212 ,  214 , as shown herein, are contiguous with the plane provided along part line  220  of the part. Sprue  218  serves as an entry location for flow of injected plastic into the mold cavity. 
   Location of the edge extremities  212 ,  214 , in an off set or spaced position from the part line of mold  216  has provided distinct advantage. Especially when the desired part is a shallow one, heretofore, the paint film, when positioned in the mold cavity, tended to shift and in some cases fell out of the mold cavity. Here, the shifting or rotation of the paint film, will be corrected by pivoting of the edgewise portion of the paint film against the extremities  212 ,  214 , which are also referred to as wrap around surfaces herein. Further, in many of the prior art processes, in which these edgewise extremities of the mold are located contiguous to the mold parting line, misaligned paint film, in accordance with the prior art processes, tended to shift into the nip between the mold parting line, and these edges were then subjected to excessive pressure forces and formed deleterious, feathered or serrated edges. 
   In accordance with the invention, the pressures encountered at the part line of the part  220  are much less than those experienced at the part line of the mold  216 , so the tendency to form feathered or serrated edges is accordingly minimized. 
   Turning now to  FIG. 4 , there is shown a magnified sectional view of a part in accordance with an invention shown in its position in the mold, prior to opening of the mold for part ejection. The view here is taken of a co-molded part in which a paint film has been fusingly bonded by the molding process over the plastic injected into the mold. Here, the edge  14  of the part is completely wrapped around or covered by paint film  16  as shown at  20 . The wrap around edge  214  of the male or core surface is coplaner and contiguous with the part line  220  of the part. 
   Another embodiment is shown in  FIG. 4   a , wherein the wrap around surface comprises a concavity  214   a  contiguous with the part line  220  of the part, spaced above the part line of the mold  216  ( FIG. 3 ). 
   In accordance with the invention, it is possible to provide parts of the type shown in  FIG. 5  wherein an angle ∝ of less than 90 degrees is provided between vertices  300 ,  302 . Vertex  300  represents a tangent touching the curved surface of the part existing on the face or show side of the part, adjacent to the left hand longitudinal edge  18  of the part  6 . Vertex  302  represents the plane presented by the edge  18  of the part. Note that the edge  18  of the part as represented by the vertex  302  is straight or planar. This edge extends parallel to the longitudinal axis  105  of the part  6  as shown in  FIGS. 6 and 7 . Accordingly, by use of the methods and mold cavity structure reported herein, the pair of longitudinally extending edges  12  and  14  are flat (not rounded) and are completely wrapped or covered with paint film  18 ,  20 . 
   Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.