Patent Publication Number: US-2011049747-A1

Title: Process for Bonding Metal Frame with Plastic Material

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a process for bonding a metal frame with a plastic material and, in particular, to a process that would increase yield rate of the product formed thereby and improve manufacturing efficiency. 
     2. Description of the Related Art 
     Some laptops use metal frames for greater value and improved quality measurement, so the laptops are more attractive to customers. But, it is difficult, time-consuming and costly to fabricate any engaging members, or locking members or positioning members on the metal frame. 
     U.S. Pat. No. 6,893,590, entitled coupling metal parts with a plastic material, teaches a process that comprises a) applying a powder of an adhesive polymer composition to the metal surface; b) overmoulding the metal surface with a plastic material by injection moulding; c) cooling the plastic material to a temperature below its softening point; d) applying heat to the metal surface, to re-soften or re-melt the plastic material in contact with the metal surface to enhance adhesion between the plastic material and the metal surface. However, cooling and re-melting the plastic material are laborious; and re-melting the plastic material increases defect rate as to the shape and positioning of the plastic material. 
     Because a laptop case only has a gross profit margin 3%˜5% and any defect would incur an increase in manufacturing cost, so it is desirable to improve the prior art in order to increase yield rate for higher gross margin. 
     The present invention is, therefore, intended to obviate or at least alleviate the problems encountered in the prior art. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a process for bonding a metal frame with a plastic material includes preparing the metal frame that is overlaid with an adhesive. The adhesive is heated thereafter, and the adhesive becomes solidified and thus engaged securely with the metal frame. The adhesive is injection molded thereafter, and the molten resin is delivered onto the solidified adhesive to melt the adhesive so as to enable the adhesive to adhere the resin, and after the adhesive and the resin become solid, the resin forms a plastic member securely bound with the metal frame, thus forming the finished product. 
     It is an object of the present invention that the process improves the yield rate of the product formed thereby and increases the manufacturing efficiency. 
     Other objects, advantages, and new features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanied drawings 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart of a process for bonding a metal frame with a plastic material in accordance with the present invention. 
         FIG. 2  is an illustrative view of a metal frame. 
         FIG. 3  is an illustrative view showing the metal frame overlaid with an adhesive thereafter. 
         FIG. 4  is an illustrative view showing the adhesive solidified and bound with the metal frame in a heating step thereafter. 
         FIG. 5  is an illustrative view showing the metal frame put in a mold of an injection molding machine thereafter. 
         FIG. 6  is an illustrative view showing a plastic material injected on the adhesive thereafter, with the plastic material melting the contacted adhesive so as to adhere the plastic material. 
         FIG. 7  shows a finished product embodying the present invention ejected out of the mold. 
         FIG. 8  is a perspective view of the finished product embodying the present invention. 
         FIG. 9  is a cross-section view of the finished product embodying the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a flow chart of a process for bonding a metal frame with a plastic material in accordance with the present invention. In this preferred embodiment, the metal frame  10  includes an inner side, an outer side opposite to the inner side, and an edge, as shown in  FIGS. 2 and 3 .  FIGS. 2 and 3  also show the inner and outer sides are substantially flat, and the edge has an inner surface extending from the inner side and an outer surface extending from the outer side, respectively, and the edge is angled with respect to the inner and/or outer sides. Further, an adhesive  20  embodying the present invention is overlaid on one of the inner and outer sides, preferably the inner side. In this embodiment, the adhesive  20  is overlaid on the inner side and the inner surface of the edge. 
     The adhesive  20  used in the present invention is a PU polymer, and the adhesive  20  is mixed with diluent, methyl ethyl ketone (MEK) in this preferred embodiment, so as to allow the adhesive  20  to be easily overlaid on the metal frame  10 . 
     Turning to  FIG. 1 , the process of the present invention includes preparing the metal frame  10  and overlaying the adhesive  20  on the metal frame  10  thereafter. After the adhesive  20  is overlaid on the metal frame  10 , the metal frame  10  is put in a heating device  30 , as shown in  FIG. 3 . During the heating step, the heating device  30  is set at temperatures between 55-65 degrees centigrade, so the adhesive  20  of liquid phase is solidified and bonded securely with the metal frame  10 . Further, the diluent, methyl ethyl ketone, is evaporated during the heating step. After the adhesive  20  is bound with the metal frame  10 , the metal frame  10  is put in a receiving area  411  of a first mold tool  41  of an injection molding machine  40 , as shown in  FIG. 5 . Preferably, the receiving area  411  defines a hollow, and the metal frame  10  is disposed in the hollow. The injection molding machine  40  includes a second mold tool  42  engagable with the first mold tool  41 , a forming section  421  protruded from a joint face, which complemently fits and contacts with a joint face of the first mold tool  41  when the first and second mold tools  41  and  42  are engaged. The injection molding machine  40  further includes a passage  422  and an ejecting member  423  extended to the forming section  421 . 
     During the injection molding step (as shown in  FIG. 6 ), the first and second mold tools  41  and  42  are engaged with each other, the passage  422  is utilized to deliver molten resin “A”. Preferably, the resin “A” is thermoplastic. Further, the forming section  421  is disposed corresponding to position of the adhesive  20 , and the molten resin “A”, which has temperatures between 160-250 degrees centigrade, is delivered onto the adhesive  20  to melt the adhesive  20 . When the adhesive  20  is melted, the adhesive  20  can bond with the resin “A”, and the resin “A” can form a shape corresponding to the forming section  421 , and the resin “A” forms a plastic member  50  after the resin “A” is solidified. Thus, the metal frame  10  is bound with the plastic member  50  to form a finished product, as shown in  FIGS. 8 and 9 . 
     After the plastic member  50  is bound with the metal frame  10 , the ejecting member  423  can extend outside the forming section  42  and grip the metal frame  10  out of the receiving area  411  of the first mold  41 . Preferably, the second mold tool  42  includes two ejecting members  423 . Preferably, the two ejecting members  423  may be disposed on different sides of the passage  422 . 
     In view of the forgoing, the process in accordance with the present invention includes preparing the metal frame  10  that is overlaid with the adhesive  20 . The metal frame  10  is put in the heating device  30  thereafter, and the adhesive  20  is heated to become solidified and thus engaged securely with the metal frame  10 . The metal frame  10  is put in the injection molding machine  40  thereafter, and the molten resin “A” is delivered onto the solidified adhesive  20  to melt the adhesive  20  so as to enable the adhesive  20  to adhere the resin “A”, and after the adhesive  20  and the resin “A” become solid, the resin “A” forms the plastic member  50  securely bound with the metal frame  10 , thus forming the finished product. 
     Therefore, the process of the present invention eliminates the problematic and time-consuming steps to cool and re-melt the plastic material as discussed in the “Description of the Related Art” by using the molten resin “A” to melt the adhesive  20  during the injection molding step. Thus, the yield rate of the finished product is improved and the manufacturing efficiency is increased. 
     Further, the diluent is used to mix with the adhesive  20  so that the adhesive  20  can be easily overlaid on the metal frame  10 . 
     Further, the diluent is evaporated during the heating step, and the adhesive  20  changes from liquid phase to solid phase, and the solidified adhesive  20  is securely bound with the metal frame  10 . 
     While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of invention, and the scope of invention is only limited by the scope of the accompanying claims.