Patent Publication Number: US-6221161-B1

Title: Apparatus for coating fibers

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates to an apparatus for coating fibers with a thermoplastic material. 
     II. Description of the Prior Art 
     In order to increase the strength and durability of molded plastic parts, it has been previously known to introduce fibers into the plastic parts. These fibers may be of any conventional material, such as fiberglass. 
     Such fibers, however, increase the strength of the molded part only when the fibers are coated with a thermoplastic material. Conversely, unless the individual fibers are completely coated with the thermoplastic material, the fibers remain flexible and not only fail to strengthen the final molded part, but may actually introduce points of weakness in the final molded part. 
     There have been previously known devices for coating elongated fibers with a thermoplastic material and, after coating the fibers, chopping the coated fibers into relatively short lengths. The chopped coated fibers are then used as the raw material for a subsequent molding operation. 
     These previously known devices, however, have not proven entirely satisfactory in use. One disadvantage of these previously known devices is that it was difficult and time consuming to load the fibers into the apparatus, which adversely affected production of the coated fibers. Similarly, these previously known devices have been able to coat only a limited number of fibers thus adversely affecting the production efficiency of the coated fibers. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides an apparatus for coating fibers with a thermoplastic material which overcomes all of the above-mentioned disadvantages of the previously known devices. 
     In brief, the device of the present invention comprises a housing defining a reservoir in which thermoplastic material is introduced. Heaters are contained within the housing in order to maintain the thermoplastic material in a molten state in the reservoir. The housing also includes an open top which is open to the reservoir. 
     A lid is selectively movable between an open and a closed position. In its open position, the lid is moved away from the open top of the reservoir thus exposing the reservoir. Conversely, in its closed position, the lid overlies and covers the open top of the housing and simultaneously forms a slot between the lid and housing at opposed ends of the housing. 
     An elongated wiper is secured to the lid and this wiper is dimensioned so that, when the lid is moved to its closed position, the wiper extends into the reservoir. This wiper, furthermore, is substantially parallel to the slots at the opposed ends of the housing. 
     An infeed guide bar is secured to the housing between the wiper and one of the opposed ends of the housing while, similarly, an outfeed guide bar is secured to the housing between the wiper and the other of the opposed ends of the housing. These guide bars are substantially parallel to the wiper. 
     Each guide bar, furthermore, includes a plurality of longitudinally spaced ridges. These ridges serve to separate different bundles of fibers from each other so that a plurality of fiber bundles can be processed simultaneously with each fiber bundle being separated from its adjacent fiber bundle. 
     In practice, with the lid removed, a plurality of fiber bundles are positioned across the opposed ends of the housing so that the fiber bundles extend across the guide bars and with each fiber bundle positioned in between two spaced ridges on the guide bars. The lid is then positioned over the top of the housing so that the fiber bundles extend out through the slots formed on the opposed ends of the housing. Simultaneously, however, the wiper secured to the lid submerses a midportion of the fiber bundles into the reservoir which, in turn, is filled with a thermoplastic material. Thus, as the fiber bundles are drawn from one end of the housing and to the other end of the housing, the fiber bundles submerge into and pass through the reservoir and thus into the thermoplastic material. The guide bars and wiper, furthermore, serve to spread the fibers in each fiber bundle across the guide bars while the wiper forces the thermoplastic material into the fibers and ensures each fiber in each bundle is coated with the thermoplastic material. 
     After the fiber bundles are drawn through the housing, the thermoplastic material cools and hardens and the resulting coated fibers are then chopped into lengths for subsequent use in a molding operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which: 
     FIG. 1 is an elevational view illustrating a preferred embodiment of the present invention; and 
     FIG. 2 is a side sectional view illustrating the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
     With reference first to FIGS. 1 and 2, a preferred embodiment of the apparatus  10  for coating fibers is there shown and comprises a generally rectangular housing  12 . The housing  12  defines a reservoir  14  closely adjacent one end  16  of the housing while a bottom wall  18  of the housing  12  slopes upwardly from the reservoir  14  toward the other end  20  of the housing  12  for a reason to be subsequently described. 
     With reference now particularly to FIG. 2, the reservoir  14  is adapted to be filled with a thermoplastic material, such as polypropylene, and any conventional means  22  is employed to maintain a preset level  24  in the reservoir  14 . Electrical heating elements  26  are also provided in the housing  12  both around the reservoir  14  as well as under the upwardly slanting bottom wall  18  of the housing  12  in order to maintain the thermoplastic material in a molten state. 
     With reference again to FIGS. 1 and 2, an infeed guide bar  30  is secured to the housing  12  adjacent its end  16  so that the guide bar  30  extends generally parallel to the housing end  16 . Similarly, an outfeed guide bar  32  is also secured to the housing  12  so that the outfeed guide bar  32  is generally parallel to the infeed guide bar  30 , but spaced from the infeed guide bar  30  toward the housing end  20 . 
     Each guide bar  30  and  32  is elongated and includes a plurality of longitudinally spaced raised ridges  34  and  36  (FIG.  1 ), respectively, along its length so that the ridges  34  on the infeed guide bar register with the ridges  36  on the outfeed guide bar  32 . Furthermore, the spacing between adjacent ridges  34  and  36  on the infeed guide bar  30  and outfeed guide bar  32 , respectively, are dimensioned to accommodate one fiber bundle, as will subsequently become apparent. 
     Referring now to FIGS. 1 and 2, at least one, and preferably up to four, outfeed guide rollers  38  are secured to the housing so that one guide roller  38  is positioned closely adjacent the end  20  of the housing  12 . The guide roller  38  optionally contains raised ridges but, alternatively, may be continuous and curved along its upper side. 
     Referring now particularly to FIGS. 1 and 2, the apparatus  10  of the present invention further comprises a lid  40  which is movable between an open position (FIG. 1) and a closed position (FIG.  2 ). In its open position, the lid  40  exposes the open top  13  of the housing and thus is open to both the reservoir  14  as well as the bottom wall  18 . Conversely, in its closed position (FIG. 2) the lid overlies and covers the open top  13  of the housing  12 . However, when the lid  40  is in its closed position, an elongated inlet slot  44  (FIG. 2) is formed between the lid  40  and housing  12  at the housing end  16  while, similarly, an outlet slot  46  is formed between the housing  12  and lid  40  at the opposite end  20  of the housing  12 . 
     As shown in FIG. 2, an elongated wiper  50  is secured to the lid  40  so that, when the lid  40  is moved to its closed position, the wiper  50  has a lower end  52  extending below the liquid level  24  of the reservoir  14  and in between and substantially parallel to the guide bars  30  and  32 . The wiper  50  may be fixedly secured to the housing  40  or, as shown, adjustably secured by a threaded fastener  56 . 
     Similarly, an elongated wiper  58  is also secured to the lid  40  for each outfeed roller  38  such that one wiper  58  registers with each outfeed guide bar  38 . Like the wiper  50 , the wipers  58  can be either fixedly secured to the lid  40  or, as illustrated in the drawing, adjustably secured by a threaded fastener  60 . 
     Any conventional means can be employed to move the lid  40  between its open and closed position. However, in the preferred embodiment of the invention, the lid  40  is movably mounted on tracks  62  (FIG. 1) and movable by an actuator  64  between an open and a closed position. 
     In operation, in order to coat fibers, the lid is first moved to its open position. A plurality of fiber spools  70  (only one illustrated) are than mounted adjacent the housing end  16  and one fiber bundle is positioned across the housing  12  so that one fiber bundle is positioned between each pair of adjacent raised ridges  34  and  36  on the guide bars  30  and  32 , respectively, and so that each fiber bundle extends from the housing end  16  into the housing end  20 . Although the apparatus shown in the drawing accommodates six fiber bundles, more or fewer fiber bundles can be accommodated without deviation from the spirit or scope of the invention. 
     After the fiber bundles  72  have been positioned across the housing  12 , the lid is moved to its closed position. In doing so, the wiper  50  engages the fiber bundles  72  thus forcing a portion of the fiber bundle around the wiper  50  beneath the reservoir level  24 . The reservoir  24 , in turn, is filled with a molten thermoplastic material from the source  22  and maintained in its molten state by the heaters  26 . Furthermore, with the lid  40  in its closed position, the fiber bundles  72  are positioned through the slots  44  and  46  at the opposed ends  16  and  20  of the housing  12 . 
     Any conventional means  80  (FIG. 2) can be used to engage the fiber bundles  72  as the fiber bundles  72  exit from the slot  46  and thus draw the fiber bundles  72  through the housing from the slot  44  and to the slot  46 . In doing so, the fiber bundles  72  are forced into the molten thermoplastic material contained within the reservoir  14  such that the wiper  50 , as well as the wipers  58  and guide bars  32  and  38 , force or wipe the thermoplastic material around each fiber in each bundle  72 . 
     In practice, it is desirable that the fibers in each bundle are spread apart as the fibers pass through the reservoir  14 . Consequently, a conventional clutch mechanism not shown is preferably associated with each spool  70  in order to impart longitudinal tension on each fiber bundle  72 . This tension, in turn, effectively spreads the fibers in each fiber bundle across the guide bars  30  and  32  and between the adjacent ridges  34  and  36 , respectively, thus further ensuring that all of the fibers in each bundle  72  are coated with the thermoplastic material. 
     As the fiber bundles  72  are drawn through the apparatus  10  of the present invention, the wipers  58  with their associated guide bars  38  effectively remove any excess thermoplastic material from the fiber bundles  72 . This excess material falls to the inclined bottom wall  18  of the housing  12 . Since this bottom wall  18  is heated by the heaters  26 , the excess material flows down the bottom wall  18  of the housing  12  and is returned to the reservoir  14 . Furthermore, the adjustment means  60  on the wipers  58  provides a simple means for ensuring that excess thermoplastic material is removed from the fiber bundles  72  and returned to the reservoir  14 . 
     It is known that preheating the fibers prior to their submersion in the reservoir  14  enhances complete coating of the fibers with the thermoplastic material. Additionally, the coated fiber bundles  72 , after exiting from the housing slot  46 , cure and are then chopped into smaller pieces for use as raw material in a molding operation. 
     The apparatus optionally includes means  65  (FIG. 2) for pressurizing the reservoir  14 . 
     From the foregoing, it can be seen that the present invention provides a simple and yet totally effective apparatus for coating a plurality of fiber bundles with thermoplastic material. Having described my invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.