Abstract:
A system for coating fibers having a plurality of inlet conduits configured to receive a corresponding fiber; a reservoir for holding a coating solution to be applied to fibers passing through the reservoir; a dryer for drying coated fibers exiting the reservoir; a plurality of outlet conduits configured to receive a corresponding fiber; a winding assembly for individually winding fibers exiting from the plurality of outlet conduits; a sensing device for monitoring fiber conditions including fiber speed and fiber breakage; and a control unit operatively associated with the sensing device, winding assembly and dryer.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to a coating system and more specifically to a system for coating fibers for use in dental restorative materials. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the fabrication of fiber-reinforced composite restorative materials comprising fibers impregnated in a resin, it is important that the fibers adhere strongly to the resin and that no debonding occurs. In order to assist in the bonding of the fibers to the resin, the fibers may further be treated, for example, chemically or mechanically etched, silanized, or otherwise treated such as by grafting functional monomers to obtain proper coupling between the fibers and the resin matrix. Silanization renders the fibers hydrophobic, reducing the water sorption and improving the hydrolytic stability of the composite material, renders the fibers organophilic, improving wetting and mixing, and bonds the fibers to the polymeric matrix. 
         [0003]    Current systems for coating fibers with materials such as silanes have many limitations. The processes are limited as to the number of fibers that may be put through the system, typically, not greater than two fibers at a time. Current devices do not have the ability to adjust and monitor the line tension during the process nor do they monitor line breakage. It is difficult to maintain proper fiber alignment throughout the process. 
         [0004]    It would be advantageous to provide a system that automates the fiber coating process. It would be beneficial to provide a system that monitors the fiber coating process for line breakage, tension and other factors automatically. 
       SUMMARY OF THE INVENTION 
       [0005]    These and other objects and advantages are accomplished by the coating system of the present invention that provides an automated process for coating fibers with a coupling or other material. The coating system includes a plurality of inlet conduits positioned downstream from a source of fibers, each inlet conduit configured to receive a corresponding fiber; a reservoir positioned downstream from the inlet conduits for holding a coating solution to be applied to fibers passing through the reservoir from the inlet conduits; a dryer positioned downstream from the reservoir for drying coated fibers exiting the reservoir; a plurality of outlet conduits positioned downstream from the dryer, each outlet conduit configured to receive a corresponding fiber; a winding assembly positioned downstream from the outlet conduits for individually winding fibers exiting from the plurality of outlet conduits; a sensing device disposed between the source of fibers and the winding assembly for monitoring fiber conditions including fiber speed and fiber breakage; and a control unit operatively associated with the sensing device, winding assembly and dryer. 
         [0006]    The system may further include a computer or programmable logic controller to start and stop the operation of the system and for providing a read-out of the device parameters. The winding assembly includes a plurality of finishing spools for winding the fibers thereon and a plurality of winder guides for guiding the fibers to the finishing spools. 
         [0007]    The system may further include a series of spools positioned downstream from the outlet conduits, whereby the outlet conduits are shortened and the spools are inserted to guide the fibers to the winding assembly. 
         [0008]    In a process for coating fibers provided herein, a plurality of fibers are guided through a plurality of inlet conduits and passed through a reservoir having a coating solution therein, whereby the fibers are coated with a coating solution. Thereafter, the coated fibers are sent through a dryer whereby the coating solution is activated and the solvents are dried and subsequently passed through a plurality of outlet conduits for directing the fibers onto loading spools, upon which the fibers are wrapped. Alternatively, the outlet conduits may be shortened and a set of guiding spools may be used to guide the fibers onto loading spools of the winding assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    For the purpose of illustrating the invention, there are shown in the drawings, features which are presently preferred; it being understood, however that this invention is not limited to the precise arrangements and instrumentalities shown. Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
           [0010]      FIG. 1  is a perspective view of the fiber coating system of the present invention; 
           [0011]      FIG. 2  is an enlarged view of the fibers being pulled onto a reel; 
           [0012]      FIG. 3  is an enlarged view of sensors used in the fiber coating system; 
           [0013]      FIG. 4  is a perspective view of the fibers being pulled through the system; 
           [0014]      FIG. 5  is an enlarged view of a programmable logic controller used in the system; 
           [0015]      FIG. 6  is top plan view of a coating bath used in the system; 
           [0016]      FIG. 7  is a perspective view of the containment vessel containing the coating solution being pumped into the system; 
           [0017]      FIG. 8  is an enlarged view of the heating unit used in the process; 
           [0018]      FIG. 9  is an enlarged view of the exiting of the fibers in the process; 
           [0019]      FIG. 10  is an enlarged view of the fibers being wound on spools; 
           [0020]      FIG. 11  is an enlarged view of the fibers being wound on spools; 
           [0021]      FIG. 12  is an enlarged view of the fibers being wound on spools; 
           [0022]      FIG. 13  is an enlarged view of the incoming fibers on a spool; 
           [0023]      FIG. 14  is an enlarged view of the incoming fibers on a spool; 
           [0024]      FIG. 15  is an enlarged view of incoming fibers on a group of spools; 
           [0025]      FIG. 16  is an enlarged view of fibers exiting the heater in the process; and 
           [0026]      FIG. 17  is an enlarged view of the fibers exiting the heater in the process. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    The present invention is directed to a system for coating fibers. The system automates the fiber coating process, providing a faster, more efficient method of coating a high number of fibers. Reference is made to  FIG. 1 , which shows a system  10  for coating fibers. A series of starting spools  12  having fibers  14  thereon are positioned on a table  15  proximate system  10 . System  10  shows ten spools  12 , although more or less may be used depending on the production needs and demands. Fibers  14  may be any fiber known in the art, including, but not limited to, glass, carbon, graphite, polyaramid, or other fibers known in the art, such as polyesters, polyamides, and other natural and synthetic materials compatible with the polymeric matrix. Other examples of fibrous materials are disclosed in U.S. Pat. Nos. 4,717,341 and 4,894,012 and commonly assigned U.S. Pat. Nos. 6,039,569, 6,013,694, all which are incorporated herein by reference. The fibers may be provided as single strands, bundles of fibers or other forms known in the art. 
         [0028]    A main control unit  11  controls the operation of system  10  including the speed at which the fibers are pulled through the operation. Control unit  11  is programmed to provide instructions to the units in system  10 . Control unit  11  can be programmed by a computer. The fibers may be pulled through the operation at a speed in the range of from about 20 to about 100 inches/minute, and preferably at a speed in the range of from about 40 to about 60 inches/per minute. 
         [0029]    A plurality of conduits  16  extend from a plate or table  17  and are used to guide fibers  14  into a reservoir  20 . Conduits  16  may be of any known material such as stainless steel. A bracket  13  may be used to align conduits  16  in the proper direction of the operation. Sensors  18  are disposed proximate conduits  16  and detect the presence of fibers  14 .  FIG. 2  shows a more comprehensive view of sensors  18 . Each fiber may be monitored by a sensor  18 . Sensors  18  can detect movement of fibers  14  and also can detect the speed of the fibers traveling through the system. Sensors  18  may be any type known in the art, including, but not limited to, a proximity switch, a limit switch, a hall-effect switch, an electro-mechanical switch, a motion switch, a magnetic sensor, a thermocouple sensor or an optical sensor. Fibers  14  are pulled through an opening  19  in table  17  and guided onto a bobbin or reel  21 . (See  FIG. 2 ). One way of monitoring the movement and speed of fibers  14  is to monitor the movement of bobbin  21 . As fibers  14  are pulled through the system pathway, bobbins  21  are rotated. Bobbins  21  may include an opening  23  therein. As bobbin  21  rotates, opening  23  passes through sensor  18  at each rotation. As a result, sensor  18  can sense movement of bobbin  21 . Should a fiber break, bobbin  21  stops rotating and sensor  18  detects the absence of movement of bobbin  21 . Alternatively, should the speed of the fiber increase or decrease, sensor  18  shall detect such change in speed. Sensor  18  sends a signal to control unit  11  via a sensor  22 . It is preferable that sensor  18  is a mechanical sensor that senses the movement of bobbin  21  and that sensor  22  is an electronic sensor such as an LED photo light admitting diode sensor.  FIG. 3  show sensor  22 . Control unit  11  will respond to the signal by shutting down the operation of system  10 , or altering the speed of the fibers, respectively.  FIG. 4  shows fibers  14  being pulled through system  10 . 
         [0030]    A programmable logic controller or PLC  41 , is used to start and stop the operation. PLC  41  provides output for the speed of the fibers and the number of feet wrapped around spools  34  located at the end of the operation. PLC  41  is connected to control unit  11 .  FIG. 5  shows a more comprehensive view of PLC  41 . 
         [0031]    Coating bath or reservoir  20  is recessed in table  24  and retains a coating solution  25  for coating fibers  14 . By positioning reservoir  20  into table  24 , the fibers  14  maintain alignment more easily.  FIG. 6  shows a more comprehensive view of reservoir  20 .  FIG. 7  shows containment vessel  39 , which contains coating solution  25 , which is pumped into reservoir  20  by pump  27 . Pump  27  may be a peristaltic pump that continuously re-circulates the coating solution from reservoir  20  to containment vessel  39 . Reservoir  20  includes a series of tension bars or rods  26  positioned strategically in reservoir  20  for maintaining fibers  14  in tension and for immersing fibers  14  into the coating solution  25 . Bars  26  may be positioned strategically at any point to obtain immersion and tension of the fibers. Bars  26  aid in improving penetration and adhesion of the coating solution by spreading and opening the fiber bundles, exposing the filaments to the solution. 
         [0032]    Coating solution  25  may be any solution known in the art, including, but not limited to, coupling solutions such as, silanes, titanates, zirconates, aluminates, etc. It is preferable that the coating solution is a silane solution such as gamma-methacryloxypropyltrimethoxysilane, or commercially available A-174 (p-methacrylate propyl tri-methoxy silane), produced by OSI Specialties, N.Y. Silane treatment improves resin wetting of the fibers to increase adhesion of resins to the fibers. 
         [0033]    Adjacent reservoir  20  is a heating unit  28  for drying the coating solution  25  on fibers  14 . Fibers  14  are dried at a temperature in the range of about 100 to about 200° F., depending on the coating solution applied thereto. If a silane solution is used, the temperature of the drying unit is preferably in the range of about 120 to 170° F., and more preferably, 140 to 160° F. Heating unit  28  contains a series of tension bars  29  for maintaining fibers  14  in tension and for increasing the amount of time that fibers  14  may be exposed to heat. Tension bars  26  in reservoir  20  and tension bars  29  in heating unit  28  may contain grooves therein to assist in the alignment of fibers  14 . A temperature control unit  30  controls the temperature in heating unit  28 . One example of a source of heat is a digital fan that generates an air current directed over heating elements. A thermostat monitors and maintains the temperature within a few degrees Fahrenheit.  FIG. 8  shows a more comprehensive view of heating unit  28 . 
         [0034]    Upon exiting heating unit  28 , fibers  14  are guided by conduits  31 , shown in  FIG. 9 , to a winder assembly  32  more closely shown in  FIGS. 10 and 11  Winder assembly  32  may be positioned at an angle to assist in the alignment of fibers  14  and minimize variances in the tension in each line. Brackets  33  and  35  may be used to position conduits  31  adjacent heating unit  28  and guide fibers  14  to winder assembly  32 . Winder assembly  32  contains a series of spools  34  for winding the coated fibers thereon. Winder guides  36 , more closely shown in  FIG. 12 , guide fibers  14  onto spools  34 . Winder guides  36  move back and forth along a bar  37  depositing fiber  14  onto spool  34 . Fibers  14  are pulled through the system by rotation of spools  34 , which are controlled by a motor  38 . Motor  38  may be a servo motor. Motor  38  can provide greater or lesser torque for pulling fibers  14  depending on how much force is needed to maintain fibers  14  in tension. The torque may be modified by varying the gear ratio of the motor. One example of providing a greater amount of torque is to provide a gear ratio of 4:1. This will generate a greater amount of torque which will improve the pull of fibers  14  by generating a smoother pull and assist in controlling a consistent metering of fibers  14  through the cycle. A motor  40  moves winder guides  36  back and forth along the perimeter of spools  34  to guide fibers  14  onto spools  34  in a consistent and even pattern. 
         [0035]    In addition to tension bars  26  and  29  and in order to minimize line slippage and add additional tension to fibers  14 , tension devices  42  may be positioned in the system. One example of placement of tension devices  42  is proximate sensors  18 . In this way, tension is maintained at both ends of the line. The tension device may include a series of stainless steel slip washers that keep a very minimal amount of tension proximate to the sensors to prevent slippage of the fibers. 
         [0036]    Alternatively, conduits  16 s, which are used to guide entering fibers, may be shortened as shown in  FIGS. 13 ,  14  and  15 . Compared to  FIG. 1 , which shows the conduits  16  extending all the way to bracket  13 , the conduits  16 s are positioned proximate bobbin  21  and extend a short distance through bracket  43  and appear again in bracket  13 . Moreover, after the fibers exit heating unit  28 , they may be directed onto spools  42  shown in  FIGS. 16 and 17  from shortened conduits  31 s. If spools  42  are used, the conduits  31  are shortened to a length  31 s to provide for spools  42 . By shortening conduits  16  and  31 , and adding spools  42  the tension or stress in the fibers may be lessoned. 
         [0037]    The resulting fibers can be used in dental composites and dental restorations including but not limited to fillings, orthodontic retainers, orthodontic wires, bridges, space maintainers, tooth replacement appliances, dentures, crowns, posts, jackets, inlays, onlays, facings, veneers, facets, implants, abutments, cements, bonding agents and splints, to provide optimal handling properties, good wear resistance and high strength. 
         [0038]    As will be appreciated, the present invention provides an automated system for applying a coating to fibers. 
         [0039]    While various descriptions of the present invention are described above, it should be understood that the various features can be used singly or in any combination thereof. Therefore, this invention is not to be limited to only the specifically preferred embodiments depicted herein. 
         [0040]    Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is accordingly defined as set forth in the appended claims.