Abstract:
An improved rocker panel on side sill construction includes a substantially planar horizontal top portion, a side portion with a substantially convex show surface and a substantially concave hidden surface opposite the show surface, and a clip house mounting structure disposed on the hidden surface. The improvement consists of joining the clip house to the rocker panel or side sill at the juncture formed between the top show surface and side show surface of the part. Preferably, this joint comprises at least one hollow channel surrounded by a reinforcing rib connecting to the hidden surface proximate the juncture of the top portion with the side portion and connecting the clip house mounting structure to this rib. The channel and reinforcing rib may run substantially longitudinally the length of the rocker panel. The channel and reinforcing rib inhibiting sagging in the top portion of the part between adjacent clip house mounting structures. The rocker panel or side sill may be made by gas-assisted injection molding wherein a mold including a mold cavity having the desired final shape, including one or more channel cavities, is provided. A predetermined amount of thermoplastic material is then injected into the mold cavity. Gas is injected into the one or more channel cavities at a predetermined pressure. The thermoplastic material is then allowed to set while the gas pressure is maintained.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of application Ser. No. 10/068,438 filed Feb. 6, 2002 now abandoned. The disclosure of the above application is hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention pertains to molded plastic parts for attachment to a supporting member. More specifically, the present invention relates to clip house mounting structures which provide improved flexural characteristics and structural strength in the corresponding part. 
     Injection molded plastic parts are commonly used in the automotive industry for side panels, spoilers, dashboards, armrests, wheel covers, filler panels, trim pieces, bumpers, side-sill garnishes, rocker panels and the like. Typically these parts are provided with a painted, or other decorative surface such as by means of film lamination techniques. In such film lamination techniques, a paint film laminate is co-molded over an external show face surface of the plastic part. The film laminate is typically pre-formed, inserted into a mold cavity, and a thermoplastic resin is injected under pressure into the mold cavity against the backside of the laminate. The result is a plastic part having a film laminate co-molded over a plastic substrate. Laminated paint films are detailed in U.S. Pat. No. 5,514,427, the entire disclosure of which is incorporated by reference herein. Techniques for preforming paint film laminates and insert molding film-plastic parts are disclosed in U.S. Pat. No. 5,599,608, the disclosure of which is incorporated herein by reference. 
     These plastic parts are typically provided with a series of integrally molded attachment means for securing the part to the given support member. Structural strength of the attachment means is dependent upon the thickness of the plastic at the intersection of the attachment means with the remainder of the part to be supported. Thick plastic sections tend to impose shrink lines and sink marks in the show face surface when the plastic solidifies. U.S. Pat. No. 6,171,543, the disclosure of which is incorporated herein by reference, provides a reinforcing rib interposed between the connection of the clip house structure and the hidden side of the corresponding plastic part. The rib provides the required strength while limiting the thickness of plastic material proximate the show face surfaces of the part. Thereby, formation of shrink lines and sink marks in the show face surfaces, due to plastic shrinkage, are minimized. 
     In some elongated, injection molded automobile parts such as a rocker panels and side sill garnishes, excessive sagging has been noted along the top substantially planar horizontal portions of the part that are located between adjacent clip house mounting structures. Although applicant is not bound to any theory as to the reason for such sagging, it is thought that same occurs due to shrinkage of the plastic after the molding step. Accordingly, there is a need in the art to provide improved structure for attachment of the clip house to the part so as to inhibit sagging or plastic warpage between these clip house structures along the length of the part. 
     SUMMARY OF THE INVENTION 
     The rocker panel with clip house mounting structure includes a first joint connecting the part to the clip house. This joint may be in the form of a rib or the like and connects a support leg of the clip house to the juncture formed between the top show portion of the part and a depending side show portion of the part. 
     A second joint may be provided to connect the part and clip house. This may be positioned along the top of the part at a location that is transversely spaced from the first joint relative to a longitudinal axis extending along the elongated part. 
     The improved rocker panel construction may be made by a method comprising the steps of providing a mold having at least a female mold member and a male mold member wherein the female mold member is substantially concave and has a top show surface, a front show surface, and a bottom show surface. The male mold member is substantially convex and has a top hidden surface, a front hidden surface, a bottom hidden surface, and a sprue for injecting plastic. The female mold member and the male mold member cooperate to define a mold cavity with the female mold member and male mold member further cooperating to define a channel cavity running substantially along the longitudinal length of the mold cavity. A predetermined amount of thermoplastic resin is injected through the sprue into the mold cavity. Optionally, as is well known in the art, an inert gas is injected under pressure into the thermoplastic whereby channels are formed in the rib members. The thermoplastic resin is then allowed to cure or set. 
     As a preliminary step, a pre-formed film laminate may be inserted into the mold prior to the injection of the thermoplastic resin so that the thermoplastic resin flows onto the back of the laminate and presses a show face surface of the laminate against the show surfaces of the female mold member. 
     Other objects, benefits and advantages of the invention will be apparent from the following detailed description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a transverse cross-sectional view of a rocker panel made in accordance with the prior art depicting the bottom leg of the clip house structure connected at the juncture of the side portion of the rocker panel and the bottom portion; 
         FIG. 2  is a rear elevation view of a longitudinal section of the rocker panel made in accordance with the prior art depicting the sag in the substantially planar horizontal top portion that may exist between adjacent clip house mounting structures of the part; 
         FIG. 3  is a transverse cross-sectional view of a rocker panel made in accordance with the instant invention depicting the clip house structure connection at the juncture of the top portion and the side portion of the rocker panel; 
         FIG. 4  is a transverse cross-sectional view of a mold used to injection mold the rocker panel of  FIG. 3 ; 
         FIG. 5  is a transverse cross-sectional view of a second embodiment of a rocker panel made in accordance with the present invention; 
         FIG. 6  is a transverse cross-sectional view of a mold used to injection mold the rocker panel of  FIG. 5  shown at that portion of the mold corresponding to a plane through the rocker panel taken between adjacent clip house mounting structures; 
       and,  FIG. 7  is a transverse cross-sectional view of a mold used to injection mold the rocker panel of  FIG. 5  shown at that portion of the mold corresponding to a line through the rocker panel taken through a clip house mounting structure. 
     
    
    
     The invention will be further described in the following detailed description. 
     DETAILED DESCRIPTION 
     Referring initially to  FIGS. 1 and 2  there is shown a rocker panel  5  in accordance with the prior art. The rocker panel  5  is shown with a clip house mounting structure  10  connected thereto. Additionally, the rocker panel  5  is shown with the foot  15  of a person positioned as anticipated on top of the top portion  20 . With further reference to  FIG. 2 , the top portion  20  is shown to have a sag, reflected by line  22 , from its desired profile as reflected by dashed line  21 . 
     As can be seen from viewing  FIG. 1 , each clip house mounting structure  10  includes a clip mounting member  30  having a clip receiving means  35 , an upper portion  40 , and a lower portion  45  presenting a substantially planar clip mounting surface  50 . The clip house mounting structure  10  further has a horizontal member  55  extending from the lower portion  45  of the clip mounting member  30  to a reinforcing rib  60 . The reinforcing rib  60  is connected to a curved side panel  25  or skirt with foot portions  70 ,  75 . The foot portions  70 ,  75  cooperate with a portion of the side panel to define a channel  65 . 
     As can be seen in  FIG. 2 , the rocker panel  5  with clip house mounting structures  10  connected as shown in  FIGS. 1 and 2  and as described above, is subject to sagging of the top portion  20  between adjacent clip house mounting structures  10 . Sagging of the top portion  20  is thought to occur by reason of the difference in plastic shrinkage in the area around the clip house mounting structure  10  connections compared with the shrinkage of the unsupported portions of the top portion  20  between adjacent clip house mounting structures  10 . 
     Turning now to  FIG. 3  there is shown a rocker panel  105  with clip house mounting structure  110  in accordance with the present invention supporting a top portion  120  and a convex side show portion  125  or skirt of the rocker panel. The clip house mounting structure  110  has a clip mounting member  130  with a fastening means  135  located near the upper portion  140 , a lower portion  145  and a mating surface  150 . As depicted in  FIG. 3 , the rocker panel  105  is attached to a support member  131  of the auto or truck frame. The support member  131  has a lower portion  146  and a mating surface  151 . Most preferably, the mating surfaces  150 ,  151  adjoin one another when the rocker panel  105  is fixed to the supporting member  131 . 
     With further reference to  FIG. 3 , the clip house mounting structure  110  further includes a first structural support member  155  extending from the lower portion  145  of the clip mounting member  130  to the reinforcing rib  160  that is located at the juncture of the top surface with the side show surface. The reinforcing rib  160  has foot portions  170 ,  175  which cooperate with the juncture of the top portion  120  and the side portion  125  to define a channel  165 . The reinforcing rib  160  and channel  165  extend longitudinally along substantially the entire length of the rocker panel  105  and provide increased flexibility of the part especially at those locations in which the rocker panel is connected to the clip house. The reinforcing rib  160  provides a strong connection for the structural support member  155  while facilitating minimal plastic thickness in any one area. The upper portion  140  of the clip mounting member is connected to the edge of the top portion  120  along surface  183 . 
     In the preferred embodiment of rocker panel  105 , the clip house mounting structure  110  includes a web  200  for additional structural strength. The web  200  is preferably connected along the edge  205  to an inner surface  210  of the structural support member  155  and along the edge  215  to an inner surface  220  of the clip mounting member  130 . As shown, the web  200  may also be connected to the part along edge  225  to a top portion hidden surface  230  as shown at surface  183 . The web  200  may be connected along a portion of its edges  205 ,  215 ,  225 , as opposed to the entire edge. 
     As can be seen in  FIG. 3 , taken in contrast to  FIG. 1 , the junction or joint connecting the clip house to the show side surface or skirt of the rocker panel in accordance with the invention, is located at a portion wherein the top surface  120  of the rocker panel joins the side show surface  125  of the part. In contrast, the prior art device shown in  FIG. 1  is such that the clip house is joined to the side show surface of the part at the approximate mid-length of the side show surface or skirt. The structure shown in  FIG. 3  provides a fulcrum located between the top surface of the rocker panel and its side show surface to allow for bending action around this juncture. Preliminary test runs demonstrate that molded parts having a clip house structure such as that shown in  FIG. 3  do not tend to exhibit the sagging type structure between adjacent clip houses as shown in  FIG. 2 . 
     Turning now to  FIG. 4 , there is shown a sectional view of mold  300  for making the rocker panel  105  in accordance with the present invention. The mold  300  includes a female mold member  305 , a male mold member  310  and a bottom mold member  315  defining a mold cavity  320 . The precise number and arrangement of mold members will depend upon the desired shape of the rocker panel  105 , or other part, the thermoplastic material used, and the type of injection molding process used. Although a three part mold is shown, the part could easily be made in a two part mold. The mold cavity  320  is further defined by a substantially convex show face surface  340 , a substantially convex hidden surface  330 , a top show face surface  335 , a top hidden surface  350 , a rib forming space  365  with corresponding elongated depression  370 , and a sprue  375  in fluid communication with cavity  320  through space  365 . The show face surface  340  includes a side portion  325  and a bottom portion  345 . The hidden surface  330  includes a side portion  355  and a bottom portion. 
     A preferred method of making the rocker panel  105  of the present invention comprises providing the mold  300  of  FIG. 4 , including a show surface  340 , a hidden surface  330 , and a mold cavity  320  defined by the show surface  340  and the hidden surface  330 , a channel-defining surface  370  contiguous with the hidden surface  330  defining a channel cavity  365 , and a sprue  375  in fluid communication with the channel cavity  320 , injecting a predetermined amount of thermoplastic resin under pressure through the sprue  375  into the mold cavity  320 , stopping the flow of thermoplastic resin, injecting a predetermined amount of nonreactive gas under pressure through the sprue  375  into the channel cavity  320 , allowing the thermoplastic resin to cure or set, and removing the cured thermoplastic resin from the mold. 
     To remove the rocker panel  105  from the mold  300 , the bottom mold member  315  is first lowered from the completed rocker panel  105 . The female mold member  305  is then separated from the male mold member  310  to reveal the rocker panel  105 . Next, the portion of the male mold member  310  containing the sprue  375  may be separated from the rocker panel  105 . If need be, the male mold member  310  may be withdrawn from the rocker panel  105  in sections to free the complex shape of the clip house mounting structure  110 . If desired, the mold  300  may be provided with a cutting member (not shown) for separating the sprue material from the rocker panel  105  or venting the gas from the channel  165 . 
     Viewing  FIGS. 4 and 3 , the method of the preferred embodiment produces the rocker panel  105  (see  FIG. 3 ) having the channel  165  surrounded or defined substantially by the foot portions  170 ,  175  of the reinforcing rib  160 . The channel  165  and the reinforcing rib  160  connect the lower portion  145  to the hidden surface  330  using the structural support member  155  such that the reinforcing rib  160  effectively branches or divides into two feet  170 ,  175  joined to the hidden surface  330 . 
     The thickness of the reinforcing rib  160 , the type and amount of thermoplastic material, and the gas pressure are chosen such that the thermoplastic material cures without producing sink marks in the show surface  340  opposite the feet  170 ,  175 . Preferably, the channel  165  and reinforcing rib  160  run substantially along the entire length of the rocker panel  105 , but may be limited to shorter runs, or even confined to an area immediately under the clip house mounting structures  110 . 
     Suitable thermoplastic resins that may be used in the process of the instant invention include, without limitation, thermoplastic olefin and acrylonitrile butadiene-styrene. Additional suitable thermoplastic materials may include, for example, polyvinyl chloride, polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate-glycol, nylon, and RIM urethanes. Polyolefin homopolymers and copolymers are inexpensive thermoplastic resins which have excellent molding properties and may also be mentioned as being suitable for use. 
     In accordance with the invention, it is preferred to use gas-assisted injection molding techniques such as “full shot” injection molding. Alternatively, the improved rocker panel of the instant invention may be molded by means of a “short shot” method wherein a predetermined amount of thermoplastic material is first injected into the mold cavity, and then a predetermined amount of a gas is injected simultaneously with the remaining amount of thermoplastic material necessary to fill out the mold. While nitrogen is the preferred gas for use in gas-assisted injection molding, other inert or relatively nonreactive gases may be used as well. 
     In addition, as a preliminary step, a laminate such as, for example, a paint film laminate, may be preformed and inserted into the mold prior to the step of injecting the thermoplastic resin such that the thermoplastic resin is deposited against a rear surface of the laminate thereby pressing a show surface of the laminate against the show surface of the mold. The resulting plastic part has a show or decorative surface fused or bonded over a plastic substrate, and is substantially free of sink marks and other undesired depressions. 
     Referring now to  FIG. 5 , another rocker panel  405  is shown. Rocker panel  405  includes first reinforcing rib  460  and a second rib  490  extending longitudinally along opposing edges of the top portion  420 . Rocker panel  405  includes clip house mounting structures  410  supporting a top portion  420  and a convex side portion  425 . The clip house mounting structure  410  has a clip mounting member  430  with a fastening means  435  located near the upper portion  440 , a lower portion  445  and a mating surface  450 . 
     With further reference to  FIG. 5 , the clip house mounting structure  410  further includes a structural support member  455  extending from the lower portion  445  of the clip mounting member  430  to a first reinforcing rib  460 . The first reinforcing rib  460  has foot portions  470 ,  475  which cooperate with the juncture of the top portion  420  and the side portion  425  to define a channel  465 . The rib  460  and channel  465  extend longitudinally along substantially the entire length of the rocker panel  405  and impart rigidity and sag resistance to the top portion  420 . The reinforcing rib  460  provides a strong connection for the structural support member  455  and provides a fulcrum for flexing of the surfaces  420  and  425  around the axis of the channel formed in the rib. The upper portion  440  of the clip mounting member is connected to a second reinforcing rib  490 . 
     In the embodiment shown in  FIG. 5 , the clip house mounting structure  410  includes a web  500  for additional structural strength. The web  500  is preferably connected along the edge  505  to an inner surface  510  of the structural support member  455  and along the edge  515  to an inner surface  520  of the clip mounting member  430 . The web  500  may also be connected along edge  525  to a top portion  120  hidden surface  530 . The web  500  may be connected along a portion of its edges  505 ,  515 ,  525 , as apposed to the entire edge. 
     Turning now to  FIGS. 6 and 7 , there is shown sectional views of mold  600  for making the rocker panel  405  in accordance with the present invention.  FIG. 6  depicts a section taken through the mold  600  between clip house mounting structures.  FIG. 7  depicts a section taken through the mold  600  at the location of a clip house mounting structure. The mold  600  includes a female mold member  605  and a male mold member  610  defining a mold cavity  620 . The precise number and arrangement of mold members will depend upon the desired shape of the rocker panel  405 , or other part, the thermoplastic material used, and the type of injection molding process used. Although a two-part mold is shown, the part could easily be made in a three-part mold. The mold cavity  620  is further defined by a substantially convex show face surface  640 , a substantially convex hidden surface  630 , a top show face surface  635 , a top hidden surface  650 , a first rib forming space  665  with corresponding first elongated depression  670  and a sprue  675  in fluid communication with cavity  620  including second rib forming space  680 . The show face surface  640  includes a side portion  625  and a bottom portion  645 . The hidden surface  630  includes a side portion  655  and a bottom portion  660 . The mold cavity  620  is further defined by a clip mounting member cavity portion  695  ( FIG. 7 ) and structural support member cavity portion  700 . The cavity portion  695  is defined by mating surface  710  and inner surface  705 . The cavity portion  700  is defined by outer surface  720  and inner surface  715 . 
     The method of making the rocker panel  405  as illustrated in  FIGS. 6 and 7  of the present invention comprises providing the mold  600  of  FIGS. 6 and 7 ; injecting a predetermined amount of thermoplastic resin (not shown) under pressure through the sprue  675  ( FIG. 6 ) into the mold cavity  620 ; stopping the flow of thermoplastic resin; injecting a predetermined amount of nonreactive gas (not shown) under pressure through the sprue  675  into the first and second rib-forming spaces  665 ,  680  to generate gas pressure in those spaces; solidifying the resin by allowing it to cure or set in the mold cavity  620  under controlled temperature conditions while maintaining the gas pressure in the first and second rib-forming spaces  665 ,  680 ; and removing the cured thermoplastic part  405  from the mold  600 . A paint film laminate (not shown) may be positioned along the show surface  640  of the mold cavity  620  before the resin is injected into the mold cavity  620  to form a decorative surface on the finished rocker panel  405 . 
     Thermoplastic resins suitable for use in making the rocker panel  105  ( FIG. 3 ) are likewise suitable for making the rocker panel  405  ( FIG. 5 ). The finished rocker panel  405  ( FIG. 5 ) is removed from the mold  600  in a manner similar to that in which the rocker panel  105  ( FIG. 3 ) is removed from the mold  300  ( FIG. 4 ). 
     The addition of the second reinforcing rib  490  improves the attachment of the clip house mounting structure  610  to the top hidden surface  530  and further strengthens the rocker panel  405  against deflection when installed on an automobile (not shown) in a manner similar to the manner in which the rocker panel  105  is installed on an automobile, as shown in  FIG. 3 . 
     The preceding description and accompanying drawings are intended to be illustrative of the invention and not in any sense limiting. Various other modifications and applications will be apparent to those skilled in the art without departing from the true spirit and scope of the invention as defined literally by the claims and their equivalents.