Abstract:
A process for making a molded running board assembly for installation on a vehicle includes blow molding the body of the running board and incorporating one or more additional components such as a step plate or a trim strip. The process involves placing the insert into the blow mold cavity in a subcavity, holding the insert by vacuum pressure and then extruding and blow molding a parison to simultaneously mold the running board and integrate the insert.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a method of producing a running board for a motor vehicle. In particular, the invention relates to a method of creating a running board which includes a step plate and optionally one or more trim inserts.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many motor vehicles which are mounted on large wheels and tires or have raised suspension systems, have a vehicle floor which is well above the road surface on which the vehicle travels. Many such vehicles are provided with a step to facilitate entry into the vehicle. These are often referred to as a running board. Typically, running boards are used on trucks or sport utility vehicles or the like. The running board provides a structural step which projects outwardly from the rocker panel area of the vehicle and gives enough supporting surface area to support the foot of a person desiring entry or exit from a vehicle. The running board may be a separate structure from the rocker panel and requires structural support to support the load of the person standing on the running board when entering or leaving the vehicle. The running board, when installed, will have an upper supporting surface on which the person using the running board, steps. The surface extends along the length of the running board but may be relatively narrow. Accordingly, it is desirable that the surface on which the user steps, includes a step pad. The step pad may include raised portions to provide a traction aid to help resist slipping of the user&#39;s foot off the surface as the user applies weight to their foot. The step pad may also include patterns of raised and lowered areas, ribs and the like which provide a pleasing visual appearance to the installed running board.  
         [0003]     A running board has an outer surface which is highly visible, extending between the front and rear wheels of the vehicle. It is often desirable to include one or more trim strips which may extend along portions of the running board to enhance the appearance of the running board and the vehicle on which the running board may be installed.  
         [0004]     The blow molding procedure is a very cost efficient way of producing items which have a hollow structure and may be used to produce items requiring structural strength such as running boards. Accordingly, it is desirable to use the blow molding process to create such running boards.  
         [0005]     In order to meet all of the desired criteria of appearance, structural strength and anti-slip characteristics, running board assemblies may include a pluralities of parts. These may include the running board itself, a step pad and one or more trim pieces.  
         [0006]     It would be desirable to create a subassembly including all of these components for manufacture by an automotive equipment supplier for shipment to automotive assembly plants where the running board subassembly may then be assembled to the vehicle.  
         [0007]     Accordingly, there exists a need to produce the components for such a subassembly and to create the subassembly in a commercially economic fashion.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with this invention, a process for making, a running board assembly of a running board and an insert comprises providing complimentary mold components having respective molding cavities. At least one of the mold components has at least one insert subcavity within the cavity of that mold component. The process includes providing an insert. The process further includes inserting the insert into the subcavity and applying vacuum pressure into the subcavity to hold the insert in place. A parison is then extruded between the mold components. The mold components are closed and the parison is expanded within the closed cavity of the mold components to simultaneously mold the running board and to integrate the insert and the running board to produce the running board assembly.  
         [0009]     In accordance with one aspect of the invention, the insert is a step plate.  
         [0010]     In accordance with another aspect of the invention, the insert is a trim piece.  
         [0011]     In accordance with a particularly preferred embodiment of the invention, the step plate is formed of a moldable, anti-slip material which is compatible for thermal bonding with the parison. In a further preferred aspect of the invention, the process includes the step of expanding the parison so that the parison contacts the moldable step plate to raise its temperature to a temperature suitable for molding. The process further includes expanding the parison to force the moldable step plate against a molding pattern within the subcavity to mold a surface of the step plate and at the same time incorporate the step plate into the running board formed from the parison.  
         [0012]     In accordance with a further aspect of the invention, the step plate may be formed from a metallic material and the step plate includes at least one key shaped rib. In accordance with a preferred embodiment of this aspect of the invention the process includes the step of blow molding the parison against the metallic step plate so that the key shaped rib is encapsulated within the molded parison.  
         [0013]     In accordance with another aspect of the invention, the insert is a trim strip which is not thermally bondable with the parison. In a preferred embodiment of this aspect of the invention, the subcavity includes an undercut around at least a portion of the perimeter of the subcavity so that upon expansion of the parison, a portion of the parison may flow into the undercut.  
         [0014]     Various other aspects and objects of the invention may be understood from reference to the following description of preferred embodiments of the invention and the following drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a top perspective view of a running board assembly in accordance with a first embodiment of the invention;  
         [0016]      FIG. 2  is a cross section through the running board assembly of  FIG. 1  taken along the lines  2 - 2  shown in  FIG. 1 ;  
         [0017]      FIG. 3  is an expanded view of a portion of the cross-section illustrated in  FIG. 2 ;  
         [0018]      FIGS. 4 through 11  illustrate various steps of the process in accordance with the preferred embodiment of the invention;  
         [0019]      FIG. 12  illustrates an alternative component which may be used in accordance with the invention;  
         [0020]      FIG. 13  is a cross-sectional view of a running board assembly which makes use of the component of  FIG. 12  which may be manufactured in accordance with the invention;  
         [0021]      FIG. 14  is a cross-sectional view similar to  FIG. 4  showing an alternate embodiment, and  
         [0022]      FIG. 15  is a cross section of a molding subcavity in accordance with another aspect of the invention for use in making the component illustrated in  FIGS. 1, 2  and  3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]      FIG. 1  illustrates a running board assembly generally at  20 .  
         [0024]     The running board assembly comprises a running board  22 , a step pad  24  and a trim strip  26 .  
         [0025]     The running board  22  has an upper support surface  30 . The step pad  24  is adhered to the supporting surface  30  in accordance with the process of this invention which is explained more fully below. The running board  20  may be formed in a blow molding procedure. From review of  FIG. 2 , it will be noted that the running board includes a plurality of recesses  32  which may be formed by moving components within a blow mold in a known fashion. The recesses  32  bring the internal surface of the parison in contact with an opposite portion to form a plurality of ribs. These ribs provide the structural strength to the blow molded running board so that it meets the necessary structural requirements. Any pattern of ribs may be formed so as to provide sufficient strength to the running board  22 .  
         [0026]     The process will now be explained in greater detail with reference to  FIGS. 4 through 11 .  FIG. 4  illustrates diagrammatically the blow molding mold  40 . The blow molding mold comprises a first mold half or component  42  and a complimentary mold half or component  44 . Diagrammatically, the mold halves  42  and  44  are shown as being movable toward and away from each other by rams  46  and  48  respectively. The mold halves  42  and  44  each have supply conduits  50  and  52  respectively. The supply conduits  50  and  52  supply cooling fluids as need be. In addition, the supply conduit  52  also includes a source of vacuum pressure as will be explained more fully below.  
         [0027]     The mold halves  42  and  44  each include a mold cavity. In the view illustrated in  FIG. 4 , only the cavity  60  within mold half  44  is visible. The mold cavity  60  determines the shape of a portion of the running board and includes the necessary configuration to mold a substantial portion if not all of the support surface  30 . The mold cavity  60  within the mold half  42  also includes a subcavity  62 . The subcavity  62  includes a configuration for molding a desired pattern on what will become the upper surface of a step pad.  
         [0028]     In accordance with this aspect of the invention, a process includes providing a moldable step pad  70  and the extrusion of a parison  72 . The parison  72  may be extruded from a well known extrusion head.:  
         [0029]      FIG. 5  illustrates the movement of the step pad  70  to a position between the mold halves  42  and  44 .  FIG. 6  illustrates the movement of the moldable step pad  70  into the cavity  60  of the mold half  44 .  FIG. 7  illustrates the final position of the step plate  70  entirely within the subcavity  62 . The movement of the step pad  70  as shown diagrammatically in  FIGS. 4, 5 ,  6  and  7  can most easily be accomplished using a programmable robotic arm. A supply of step pads  70  may be located where they be grasped and extracted by one or more robot arms. The robot arm moves the moldable step pad  70  until it is placed within the subcavity  62 . Once the robot arm has placed the movable step pad  70  within the subcavity  62 , then vacuum pressure, available from supply conduit  52  is applied to the subcavity  62 , so that the moldable step plate  70  is retained and accurately positioned within the subcavity  62 . The robot arm then retracts so that it is no longer located between the mold halves  42  and  44 . When that has been completed, the parison  72  is extruded to extend between the mold halves as shown in  FIGS. 7 and 8 ,  FIG. 8  illustrates the completion of the extrusion of the parison and the mold halves are now ready to be closed about the parison.  
         [0030]      FIG. 9  illustrates the closure of the mold halves  42  and  4 . 4  to form a closed blow mold ready for application of a blow molding gas under appropriate pressure.  
         [0031]     In this embodiment of the invention, the moldable step plate  70  is made from a material which may be thermal formed within the mold  42  and which is compatible with the material of the parison  72  so that the materials may fuse together to form an integral structure under suitable pressure and temperature.  
         [0032]     The vacuum pressure applied to the submold  62  is intended primarily to hold the moldable step plate  70  in place. If the moldable step plate has not been raised to a temperature close to its molding temperature, no substantial molding of the step plate  70  will occur under the vacuum force alone. However, when the blow molding gas is supplied to the interior of the parison  72 , the parison is at a moldable temperature and the parison will then expand within the mold  40 . As the parison expands, a portion of the parison will then come into contact with the moldable step plate  70 . This will result in the transfer of heat from the wall of the parison to the moldable step plate  70 . In addition, as the parison  72  continues to expand, it will deliver substantial pressure to the moldable step plate  70  and forcing it against the pattern included within the subcavity  62 .  
         [0033]     Preferably the blow molding pressure is substantial. Most preferably the blow molding pressure may be at or above 90 psi.  
         [0034]     The moldable step plate  70  as illustrated in  FIG. 4 , is a relatively thin strip of moldable plastic. The strip of plastic may be of the order of one to one and a half millimeters thick. The subcavity  62  is preferably less deep than the thickness of the strip. Preferably for a strip having a thickness of one to one and a half millimeters, the cavity may be of about one half millimeter depth. This means that upon completion of the molding, the step will project upwardly from the formed surface  30  by approximately one half millimeter or more, while the remainder of the step plate will be below and integrated into the wall of the parison. This is illustrated in  FIG. 2 .  
         [0035]     After the blow molding pressure is released, in typical blow molding fashion, the mold  40  is cooled and opened. The opened mold is shown diagrammatically in  FIG. 10  with the running board assembly  20  being shown having been ejected from the mold halves ready for trimming.  
         [0036]      5  After ejection of the molded running board assembly  20 , the running board assembly is trimmed as desired and removed from the mold. This is shown in  FIG. 11 .  
         [0037]     The running board assembly  20  shown in  FIG. 1  includes a step pad  24 . The step pad  24  is incorporated into the running board assembly  10  by means of thermal fusion between the step pad  24  and the running board  22  which occurs during the blow molding process. In accordance with an alternate aspect of the invention, the step pad need not be comprised of a moldable material nor a material that will thermally fuse with the material of the running board.  
         [0038]      FIG. 12  illustrates a step pad  124 . The step pad  124  is a metal strip. The metal strip includes a raised pattern  125  on one surface and at least one and preferably a plurality of longitudinally extending key shaped ribs  128  on the other surface.  
         [0039]      FIG. 13  illustrates in cross-section, a running board assembly  120 . The running board assembly  120  includes the step pad  124  which has been incorporated during blow molding into a running board  122 .  
         [0040]     The process for manufacturing the running board assembly  120  illustrated in  FIGS. 12 and 13  is similar to the process illustrated in  FIGS. 4 through 11 . In accordance with this aspect of the invention, the metal step pad  124  is placed within a subcavity  162  within one mold half  144  of a mold  140 .  
         [0041]     The step pad  124  may be obtained from a storage location and placed into the subcavity  162  by a computer controlled robot arm. Once the step pad  124  is placed within the subcavity  162 , then vacuum pressure is applied to the subcavity  162  holding the step pad in place.  
         [0042]     Once the step pad is held in place by the vacuum pressure, then a parison  72  is extruded between the mold halves  42  and  144 , the mold is closed and a blowing pressure is applied to the interior of the parison. As the parison expands under the blowing pressure, a portion of the wall of the parison will encounter the surface of the step pad  124  which includes the plurality of key shaped ribs  128 . The raised portions  125  of the step pad  124  will bear against the surface of the subcavity  162 .  
         [0043]     With reference to  FIG. 13 , it will be observed, that as the wall of the parison is forced under blowing pressure against the ribs  128 , a portion of the wall will flow around the ribs. Each rib is substantially key-shaped. By this, it is meant that the portion of the rib which becomes embedded in the wall of the parison has an undercut or smaller width. In a preferred embodiment of the invention as shown in  FIG. 13 , the ribs are T-shaped. When the wall of the parison solidifies as the mold is cooled, then the cooled plastic of the parison wall extends into the undercut or thinner region of the rib thereby permanently incorporating the step pad  124  into the running board  120  as the running board is formed. Thus, when the mold opens, the part which is ejected is the running board assembly  120  with an integrated step pad  124 .  
         [0044]     Reference is now made to  FIGS. 1, 2 ,  3  and  15 . As shown, the running board assembly  20  includes a trim strip  26 . The trim strip may be a moldable plastic which can thermally fuse with the parison  70  as the running board  22  is formed. Alternatively, the trim strip  26  may be manufactured from a material which does not thermally fuse with the running board  20 . In this regard, the trim strip  26  may be a metallic strip similar to the step pad  124 .  
         [0045]     The trim strip  26  is in the form of an insert which may be positioned within a mold half  43  in a manner analogous to the step pad  70  or the step plate  124 . In order to accomplish this, there may be a separate subcavity  263 . The subcavity  263  may either be in the same mold half as the subcavity  62  or in the other mold half. While the trim strip  26  may use a similar retention means as the ribs  128  of step pad  124 , an alternate retention system is shown in the enlarged view of  FIGS. 3 and 15 .  
         [0046]     The subcavity  263  into which the trim strip  26  may be placed and retained by vacuum pressure advantageously includes an undercut  264  extending around the perimeter of the subcavity  263 . The running board assembly including both the step pad  24  or a step pad  124  and one or more trim strips  26 , may be formed using the process discussed in connection with  FIGS. 4 through 11 . As the wall of the parison is expanded toward the trim strip  26 , material from the parison will be forced against the surface of the trim strip  26 . Under the blowing pressure, a small portion  80  of the parison material will be forced into the undercut. That portion of the parison then is adjacent the other surface of the trim strip  26 . Sufficient length of undercut along the perimeter of the subcavity containing trim strip  26  is provided so that upon completion of the molding process, the trim strip  26  is permanently retained in the running board assembly  20 . Most preferably, the undercut extends substantially around the perimeter of the subcavity so that in effect, the portion  80  of the parison material flows around substantially all of the perimeter edge of the trim strip  26 . This in effect provides a permanent picture frame type retention of the trim strip  26 .  
         [0047]     The trim strip  26  is retained by the cooled material of the parison. Thus, the trim strip  26  may be manufactured from any desirable material which would include metals or plastics which are not compatible with the material of the running board  22  or materials which are compatible with the material of the running board  22 .  
         [0048]     As has been explained above, there are various aspects of preferred embodiments of the invention. The above description is to be taken as illustrative only with the full scope of the invention to be determined from reference to the following claims.