Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – With internal application of fluid pressure
Reexamination Certificate
1998-05-19
2001-01-09
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
With internal application of fluid pressure
Reexamination Certificate
active
06171543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for making improved rocker panels and rocker panels made thereby.
2. Description of the Prior Art
A variety of injection molded parts are made and used for automobile body and trim parts. For example, bumpers, spoilers, body panels, doors, filler panels, wheel covers, dashboards, armrests, and other parts are commonly made by injection molding of thermoplastic materials. In addition, side sill garnishes, rocker panels, and rocker molds may be made by the injection molding process.
These plastic parts often have attachment means on their back or hidden sides in order to affix them to or mount them on an automobile. A common method of attaching plastic parts to automotive vehicles involves providing a plurality of clip houses on the backside of the plastic part. The clip houses are often molded on the backside of the part simultaneously with the molding of the part itself. The clip houses generally provide stand off surfaces to which mounting clips are attached. The plastic part may then be mounted on the automobile by aligning the mounting clips with corresponding holes or openings in the automobile, and pressing the plastic part into position. The mounting clips thereby exert a force to positively retain the plastic part against the automobile.
Plastic parts such as rocker panels, and the like, usually must withstand greater environmental stresses than other plastic parts. Rocker panels and side sill garnishes, for example, are usually attached to an automobile body below the door opening. Because of this position, these parts are subject to being stepped on by occupants entering and exiting the vehicle, road vibration, and being struck by foreign objects and debris. Thus, plastic parts intended for these applications require significantly stronger means for attaching them to the automobiles. One common method for providing stronger clip house mounting structures is to significantly thicken the legs of the clip house. However, as injection molded plastic cures, it tends to shrink. Where the clip house leg is joined to the backside of a plastic part, the observable effects of plastic shrinkage become more pronounced. The result is the appearance of a sink mark or line on the front surface of the plastic part opposite the attachment point for the clip house leg. As the clip house leg is thickened to provide additional support, the appearance of sink marks or lines becomes more pronounced. In plastic parts where an aesthetically pleasing external appearance is desired, the appearance of sink marks or lines is undesirable.
This is especially true where plastic 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.
An additional problem with prior art methods of strengthening clip house attachment structures on plastic parts by thickening the support legs of the clip house structures is that they do not provide additional flexural rigidity to the plastic part. For example, many plastic parts, such as side sill garnishes and rocker panels, have substantial portions which are not supported along their back surfaces. These unsupported portions are subject to greater flexural deflections than adjoining supported portions. Repeated excessive flexing of the plastic parts can lead to the dulling of glossy finishes or the formation of visible cracks in external show face surfaces of the parts and may ultimately lead to fatigue and mechanical breakdown of the parts.
Accordingly, there remains a need in the art to improve the existing methods for strengthening attachment structures on the backsides of plastic parts for automobiles so as to prevent the formation of sink marks or lines on show face surfaces of the plastic parts.
Also, there remains a need in the art to improve the existing methods for reinforcing plastic parts for automobiles so as to provide for greater resistance to excessive flexing of the parts.
SUMMARY OF THE INVENTION
An improved rocker panel construction in accordance with the present invention comprises an injection molded plastic part including a substantially convex show surface and a substantially concave back or rear surface. The rocker panel may have a top show surface, a front show surface, a bottom show surface, and correspondingly a top hidden surface, a back or rear hidden surface, and a bottom hidden surface. Attachment means may comprise a clip house structure molded into the back of the rocker panel. The clip house structure includes a substantially planar clip attachment surface, a first or bottom leg connecting the clip surface to the rocker panel at the juncture where the back hidden surface adjoins the bottom hidden surface and a top or second leg connecting the clip surface to the top hidden surface. The improvement comprises a channel formed in the plastic where the bottom leg of the clip house structure joins the rocker panel such that the bottom leg essentially branches into two feet that connect to the rocker panel. Moreover, the channel runs substantially the length of the rocker panel along the joint between the back hidden surface and the bottom hidden surface.
The feet of the bottom leg substantially reduce or eliminate the occurrence of sink marks or lines in the show face surfaces of the rocker panel. Also, the channel adds strength to the structure and resists the tendency of a bottom portion of the rocker panel to flex or pivot with respect to a middle portion of the rocker panel about an axis coextensive with the juncture between the bottom portion, bounded by the bottom show surface and the bottom hidden surface, and the middle portion, bounded by the front show surface and the back hidden surface.
According to one embodiment, the rocker panel includes a show surface, a hidden surface disposed oppositely the show surface and a clip house mounting structure disposed on the hidden surface. The clip house mounting structure including a top leg and a bottom leg for connecting the clip house mounting structure to the hidden surface.
The rocker panel also includes a first reinforcing rib defining a first channel and a second reinforcing rib defining a second channel. The first reinforcing rib connects the first leg to the hidden surface while the second reinforcing rib connects the second leg to the hidden surface. Preferably, the first reinforcing rib straddles the juncture between the rear hidden surface and the bottom hidden surface to strengthen the rocker panel against flexure at that juncture. The second reinforcing rib preferably is positioned near an outer edge of said top hidden surface so as to align with the preferred position of the top leg. Where the rocker panel is formed by injection molding, the reinforcing ribs may include one or more sprue holes.
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 cavit
Biebel & French
Mason Suzanne E.
Tokai Kogyo Co. Ltd.
Vargot Mathieu D.
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