Patent Publication Number: US-2006003172-A1

Title: Composite element and method for producing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      The present application claims priority from German Patent Application DE 102004032362.3 filed on Jul. 3, 2004, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to a composite element and a method for producing such a composite element that is useful for supporting, lining, protecting, decorating, and sealing a housing, particularly for the frame or bodywork of a vehicle. More particularly, the invention relates to a composite part that includes a support component of plastic, a top component of plastic and a reinforcing component of metal disposed between the support component and the top component, and a method of making such a component.  
      A composite element and method for producing same are known, for example, from European Patent document EP 0335208 B1 and German Patent document DE 3415379 A1. These documents disclose a joint extrusion of a support component and a steel reinforcement to form an intermediate product. Then, a top component is sprayed onto the intermediate product. The disclosed production method is complicated and expensive. In addition, the total component tolerances for the composite element produced with this method are often excessively high, and undesirable surface defects can occur.  
      Therefore, there remains a need in the art for a method for producing a composite element that is cost-effective and produces products of high quality.  
     SUMMARY OF THE INVENTION  
      The above and other objects are accomplished according to the invention by the provision of a method for producing a composite element, comprising: inserting a reinforcing component into a first injection-molding section of an injection-molding tool; injection-molding a plastic support component on to the reinforcing component to form an intermediate product; moving the intermediate product to a second injection-molding section of the injection-molding tool; and injection-molding a plastic top component on to the intermediate product to form the composite element having a reinforcing component disposed between the plastic support component and the plastic top component.  
      Thus, the present invention provides a method for making the composite element in which the plastic support component and the plastic top component are produced with an injection-molding technique. The reinforcing component is inserted into the injection-molding tool and the two plastic components surrounding the reinforcing component are produced by a multi-component injection-molding process. The two plastic components are therefore combined with the reinforcing component by using the same type of process, namely the injection molding process.  
      The method of the present invention may further include the step of producing the reinforcing component with a deep-drawing technique prior to inserting the metal reinforcing component into the first injection-molding section.  
      Further, the injection-molding tool may comprise a center portion disposed between a first edge portion and a second edge portion, with the center portion being movable relative to the first and second edge portions. The first injection-molding section is defined between the center portion and the first edge portion, and the second injection-molding section is defined between the center portion and the second edge portion. The center portion is rotatable with respect to the first edge portion and the second edge portion.  
      According to another aspect of the invention, a second reinforcing component may be inserted into the first injection-molding section substantially while the intermediate product is moved into the second injection-molding section. The plastic top component is injection-molded onto the intermediate product in the second injection-molding section substantially while a second plastic support component is injection-molded onto the second reinforcing component in the first injection-molding section to form a second intermediate product.  
      According to another embodiment of the invention, the injection molding tool may have a first mold half and a second mold half rotatable relative to the first mold half, with the first injection molding section and the second injection-molding section defined between the first mold half and the second mold half.  
      According to another feature of the invention, the reinforcing component may be metal, such as steel or aluminum, or a fiber composite material. As a result, composite elements with good surface structure can be produced. Fastening elements can be formed directly onto the support component during the multi-component injection-molding process, which additionally reduces the production expenditure and furthermore makes it possible to produce a low weight composite element. The injection-molding section may be defined to have cavities such that fastening elements are formed integrally onto the support component during injection-molding.  
      In the present invention, the injection-molding tools in particular can be arranged such that at least the main portion of the necessary displacement movement is realized with a tool part that is not provided with a sprue gate. In particular, the arrangement allows a continuous production. The continuous process saves time, because several required processing steps can run simultaneously. The reinforcing component can be mass produced with low production tolerances.  
      According to another aspect of the invention, there is provided a composite element that includes a plastic support component, a plastic top component, and a reinforcing component disposed between the plastic support component and the plastic top component. The support component and the top component are injection molded onto the reinforcing component as individual components in separate mold sections.  
      According to one feature of this aspect of the invention, the support component has a first shore hardness and the top component has a second shore hardness that is less than the first shore hardness. Further, the reinforcing component may made of metal, such as steel or aluminum, or may be a fiber composite material. The composite element may further have a bonding layer located on at least one side of the reinforcing component or fastening elements formed integrally on the support component. The fastening elements may be clips. The clips may be made of polyoxymethylene. The fastening elements may be substantially C-shaped. The reinforcing component may be substantially planar, and at least some sections of the reinforcing component may be positioned between the fastening elements and the top component. The fastening elements may be completely covered by the top component and sections of the reinforcing component.  
      The composite element of the present invention can be adapted to different requirements to be met by the support component as well as the top component. The reinforcing component as disclosed results in a composite element with advantageously low coefficients of elongation. The reinforcing component can also consist of aluminum or a fiber composite material.  
      The fastening elements are formed-on integrally, thereby resulting in a low-weight composite element. In many cases, additional connecting elements can be dispensed with. With a composite element as defined, the fastening elements can be attached to the support component in such a way that the contours are not visible on the top. Fastening elements as well as other types of geometric elements can be formed on at all locations where the reinforcing component covers the support component, without the contours being visible on the surface of the top component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features and advantages of the present invention will be further understood from the detailed description with reference to the following drawings:  
      FIGS.  1  to  3  are cross-sectional views of different embodiments of the composite element of the present invention with a plastic support component, a plastic top component, and a metal reinforcing component disposed between them.  
      FIGS.  4  to  7  are schematic illustrations of a process for producing the composite element by means of an injection-molding tool with three tool parts which can be moved relative to each other.  
      FIGS.  8  to  12  are schematic illustrations of an alternative process for producing the composite element with the aid of an injection-molding tool provided with two tool parts which can be moved relative to each other. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
      FIGS.  1  to  3  show variants of a composite element  1 , using the example of a protective strip for placement around the lower edge of a passenger vehicle door. Identical parts of the different embodiments shown in FIGS.  1  to  3  are provided with the same reference numbers and will not be explained again.  
      In the following, the composite element  1  shown in  FIG. 1  is described first. The composite element  1  comprises a support component  2  of plastic. The support component  2  is snapped onto the lower section of a door/chassis element  3 . For this, the support component  2  is provided with numerous pairs of holding elements  4 ,  5 , wherein one pair is shown in  FIG. 1 . The holding elements  4 ,  5  are formed integrally onto the support component  2 .  
      The holding element  4  in each holding element pair is provided with a hook  6  which extends through and engages behind an opening  7  in the door/chassis element  3 . The hook-shaped holding element  4  is furthermore provided with a total of three spacing webs  8 , formed one above the other onto the support component  2 , which ensure a defined positioning of the support component  2  relative to the door/chassis element  3 .  
      The center spacing web  8  in this case ensures that the hook  6  remains in its position. The other two spacing webs  8  function as spacers between the support component  2  and the door/chassis element  3 .  
      In addition to the hook-shaped holding element  4 , each pair of holding elements also comprises a holding element  5 , wherein the latter partially encircles the lower section of the door/chassis element  3 . This lower section is positioned by means of support ribs  9  on the support component  2 , in the region along the door/chassis element  3  which does not contain a snap-on holding element  5 .  
      On the vehicle outside, the composite element  1  is covered with a top component  10  which also consists of plastic. Depending on the use, the plastic material used can be the same or a different type of plastic material as for the support component  2 . The top component  10  is shaped in such a way that its surface is flush with the visible outside of the vehicle chassis.  
      A reinforcing component  11  made of metal, for example steel or aluminum, is disposed between the support component  2  and the top component  10  and functions to reinforce the composite element. The reinforcing component may also be made of a fiber composite material. The reinforcing component  11  furthermore predetermines the elongation of the composite element, so that differences in the coefficients of elongation for the support component  2  and/or the top component  10  are not important. The reinforcing component  11  covers the hook-shaped holding elements  4 , thereby preventing undesirable contours of the hook-shaped holding elements  4  from being visible on the outside, through the top component  10 .  
      The composite element  1  shown in  FIG. 2  will now be described. The support component  2  is provided with integrally formed-on holding clips  12  as holding elements. Respectively two holding clips  12 , arranged one above the other, form a holding-element pair which corresponds to the holding element pair described in connection with  FIG. 1 . The holding clips  12  are open toward the door/chassis element  3 . Inserted into these holding clips  12  are clip elements  13  of polyoxymethylene (POM) with a C-shaped cross section, wherein these clip elements  13  are oriented such that the C-shape also opens toward the door/chassis element  3 , as shown in the cross section. The heads of T-bolts  14  which are welded to the door/chassis element  3  engage in these clip elements  13 . A receiving section of a sealing lip  15  is arranged between the support component  2  and the door/chassis element  3 , below the lower holding clip  12 .  
      When the door is closed, the sealing lip fits against a chassis part that is rigidly mounted to the frame and is not shown. The reinforcing component  11  shown in  FIG. 2  is a preformed metal foil with a thickness in the range of approximately 0.5 mm.  
      The composite element shown in  FIG. 3  will now be described. For this embodiment, a holding element pair comprises one embracing holding element  16  which is formed integrally onto the support component  2  and embraces the lower edge of the door/chassis element  3 . The holding element pair furthermore includes a clip element  17  that is integrally formed onto the support component  2 . The latter holds a clip bolt  18  which in turn is secured to the door/chassis element  3 . For the embodiment shown in  FIG. 3 , an adhesive tape  19  is arranged in the upper end region of the composite element  1 , between the support component  2  and the door/chassis element  3 . This adhesive tape is designed in particular to keep the composite element  1  from rubbing against the door/chassis element  3 . The reinforcing component  11  for the embodiment according to  FIG. 3  is a metal foil having a thickness of approximately 0.4 mm.  
      A first method for producing a composite element  1 , shown in FIGS.  1  to  3 , is illustrated schematically in FIGS.  4  to  7 . The method is realized by means of an injection-molding tool  20 , comprising three tool parts that can be moved relative to each other, wherein a center part  21  is positioned between two edge parts  22 ,  23 . The edge parts  22 ,  23  can be displaced relative to the center part  21 , along two double arrows shown in  FIG. 4 . When the injection-molding tool  20  is closed (as shown in  FIGS. 5 and 7 ), two first injection-molding sections  24  are defined between the center part  21  and the first edge part  22 , shown on the left in FIGS.  4  to  7 . The injection-molding sections are used for shaping a first injection-molded component of the composite element  1 , namely the support component  2 . A first sprue gate  25  extends through the left edge part  22  up to the first two injection-molding sections  24 . If the injection mold  20  is closed, two second injection-molding sections  26  are defined between the center part  21  and the second edge part  23 , shown on the right side in FIGS.  4  to  7 . These sections are used for shaping a second injection-molded component of the composite element  1 , namely the top component  10 . A second sprue gate  27  extends up to the two second injection-molding sections  26 , wherein this gate extends through the right edge part  23 . The center part  21  can be rotated around a central axis of rotation  28 , positioned perpendicular to the drawing plane for FIGS.  4  to  7 .  
      Using the three-part injection molding tool  20 , the composite element  1  is produced as follows: The injection-molding tool  20  is initially in the opened position, as shown in  FIG. 4 . Two reinforcing components  11 , produced in a preliminary step by means of deep-drawing, are inserted into the two first injection-molding sections  24 . The reinforcing components  11  are provided on both sides with a bonding layer. Bonding layers of this type are known to the person skilled in the art.  
      The two reinforcing components  11  and the first injection-molding sections  24  in the region of the left edge part  22  have complementary shapes, so that the inserted reinforcing components  11  fit flush against the left edge part  22  of the injection-molding tool  20 . Following this, the injection-molding tool  20  is closed, resulting in the closed position shown in  FIG. 5 . A first plasticized plastic material is then injected through the sprue gate  25  into the two first injection-molding sections  24  (e.g., upon the initial run of the injection-molding tool  20 ). During the initial filling of the injection-molding sections  24 , a filling of the second injection-molding sections  26 , between the center part  21  and the right edge part  23 , can be omitted. Alternatively, the second injection-molding sections  26  can be filled on the initial run, and the resulting molded part discarded. The material filling injected into the first injection-molding sections  24  initially has a temperature that is high enough to cause a response of the bonding agent in the bonding layer of the reinforcing component  11 , which is facing the plasticized plastic material. The hardening plastic material thus securely bonds with the reinforcing component  11 .  
      Since the bond between the plastic material and the center part  21  is stronger than the bond between the reinforcing component  11  and the edge part  22 , the produced composite element consisting of the reinforcing component  11  and the first injection-molding component (eventually becoming the support component  2 ) adheres to the center part  21 . In the following, this composite product is also referred to as an intermediate part or an intermediate product. The injection-molding tool  20  is subsequently moved back to the open position. The center part  21  is then rotated by 180° around the axis of rotation  28 .  FIG. 6  shows the position of the injection-molding tool  20  following completion of this rotation. In this opened position, an additional pair of reinforcing components  11  is inserted into the injection-molding sections  24  in the left edge part  22 . The injection-molding tool  20  is then closed again. Following this, plasticized plastic material is injected through the two sprue gates  25 ,  27  into the injection-molding sections  24  and  26 .  
      The first injection-molding component is again formed in the first injection-molding sections  24 , as described in connection with  FIG. 5 . The respectively second injection-molding component, meaning the top component  10 , is created in the second injection-molding sections  26  which are designed with more depth along the edges than the first injection-molding sections  24  (compare with  FIG. 7 ). In the process, the hot plasticized material which is initially filled in bonds with the reinforcing component  11  via the bonding layer. The injection-molding tool  20  is then again moved to the opened position and the composite element produced in the second injection-molding sections  26  is ejected with the aid of an injector which is not shown herein. Following this, the processing steps previously described in connection with  FIGS. 6 and 7  are repeated. During each injection-molding step, respectively one intermediate product that consists of the reinforcing component  11  and the support component  2  and one finished composite element  1 , consisting of the reinforcing component  11 , the support component  2 , and the top component  10 , is produced. The complete operation, comprising the steps of opening the injection-molding tool  20 , inserting the reinforcing components  11 , rotating the center part by 180°, closing the injection-molding tool  20 , injecting the material, and ejecting the finished composite element  1  is then repeated, preferably with timed cycles.  
      An alternative method for producing a composite element  1  as shown in FIGS.  1  to  3  with an alternative two-part injection-molding tool  29  is described in  FIGS. 8-12 . Any details corresponding to those previously described in the above, in connection with the method and reference to FIGS.  4  to  7 , will not be explained again in detail.  
      The injection-molding tool  29  comprises two tool parts  30 ,  31  which can be displaced in the direction of a double arrow shown in  FIG. 8  for an opened position as shown in  FIGS. 8, 10  and  11  and a closed position as shown in  FIGS. 9 and 12 . In the closed position, two injection-molding sections  32 ,  33  are defined between the two tool parts  30 ,  31 . In addition to being displaceable along the double arrow shown in  FIG. 8 , the right tool part  31  can be rotated around an axis of rotation  34  (shown in  FIG. 11 ) in the opened position of the injection-molding tool  29 , where this axis of rotation is positioned horizontal in the drawing and in the drawing plane.  
      The left tool part  30  contains two sprue gates  35 ,  36 . The sprue gate  35  which is shown at the top of the drawing is connected to the first injection-molding section  32  while the lower second sprue gate  36  in the drawing is connected to the second injection-molding section  33 .  
      The production of composite elements  1  by means of the injection-molding tool  29  is described in the following. A reinforcing component  11  is initially inserted into the upper injection-molding section  32  while the injection-molding tool  29  is in the opened position. This situation is shown in  FIG. 8 . The injection-molding tool  29  is then closed and the first injection-molding step takes place. As explained in the above in connection with the process illustrated in FIGS.  4  to  7 , an injection of material into the second injection-molding section  33  can be omitted during the initial injection operation (compare with  FIG. 9 ). If this injection step is not omitted, then the very first component produced in the lower injection-molding section  33  can be discarded.  
      Following the injection, the intermediate part is created in the upper injection-molding section  32 , as previously explained in connection with FIGS.  4  to  7 . The injection-molding tool  29  is subsequently returned to the opened condition, a shown in  FIG. 10 . During the opening of the injection-molding tool  29 , the intermediate part adheres to the right tool part  31 , wherein this tool part is subsequently rotated by 180° around the axis of rotation  34 , so that the injection-molding tool  29  is oriented as shown in  FIG. 11 . In  FIG. 11 , a new reinforcing component  11  is then inserted into the injection-molding section  32 . Following this, the injection-molding tool  29  is closed once more. The material-injection step is then repeated, where the intermediate product is produced in the upper injection-molding section  32  and the composite element  1  is created in the lower injection-molding section  33  (compare with  FIG. 1 ) via injection-molding. Following the opening of the injection-molding tool  29 , the finished composite element is ejected. The production cycle is then repeated as described in the above in connection with FIGS.  10  to  12 , preferably in timed cycles.  
      The injection-molding sections  24 ,  26 ,  32 ,  33  in particular can also be designed such that holding elements of the type as described in connection with the composite element  1  according to  FIGS. 1-3  are formed integrally onto the support component  2 . The injection-molding sections  24 ,  26 ,  32 ,  33  are also called mold cavities. For a different embodiment which is not shown herein, a larger number of injection-molding sections  24 ,  26 ,  32 ,  33  can also be provided for each injection-molding tool  20 ,  29 .  
      It is particularly desirable if the reinforcing component  11  of a finished composite element  1  is enclosed on all sides by the plastic components  2 ,  10  to protect against corrosion. However, an enclosure of this type is not absolutely necessary. The reinforcing component  11  can already be inserted into the first injection-molding sections  24 ,  32  while the tool part  21  and/or  31  is still rotating around the axis  28  and/or  34 .  
      It may be preferred that the support component  2  is made from a plastic material for which the shore hardness is higher than the shore hardness of the plastic material used to produce the top component  10 .  
      The reinforcing component  11  for the embodiment described herein is made of steel. However, the reinforcing component  11  can also consist of aluminum or a fiber composite material.  
      The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.